JOHNA.SEAVERNS 


3  9090  013  413  493 


Webster  Family  Library  of  Veterinary  Medicine 
Cummings  School  of  Veterinary  Medi.L  jo  at 
Tufts  University 
200  yv'estboro  Road 


OUTLINES 


EQUINE    ANATOMY, 


OUTLINES 


EQUINE    ANATOMY 

A    MANUAL 

FOR    THE    USE   OF    VETERINARY   STUDENTS   IN   THE 
DISSECTING   ROOM. 


JOHN  HENRY  STEEL,  M.R.C.V.S., 

ASSISTANT-KKMONSTRATOR    OF    ANATOMY,   EOyAT,   VKTERINART    COLI.EOK. 


NEW    YORK: 

WILLIAM   WOOD   AND    CO,   PUBLISHERS. 

27,  GREAT  JONES  STREET. 


t  >^  I 


5-74 


PREFACE. 


This  sketcli  of  tlie  Structure  of  the  Horse  is  but  an  out- 
line; the  same  subject  indifferent  aspects  bas  been  treated 
by  Chauveau  (rendered  available  to  us  by  Fleming's 
Translation),  and  by  Gamgee  and  Law  ;  and  tbe  manner 
in  which  it  has  been  executed  by  them,  in  both  cases, 
betrays  the  hand  and  touch  of  the  master.  In  those  works, 
however,  the  outline  has  been  filled  up,  and  into  the  bach- 
ground  have  been  introduced  figures  of  other  domesticated 
a,nimals,  the  beauty  of  which  draws  the  attention  away 
from  the  main  object.  The  anatomical  works  of  Pro- 
fessor Strangeways  and  of  Percivall  are  fully  appreciated 
by  the  Author,  but  he  has  found  that  a  concise  work  with 
an  arrangement  illustrating  the  sequence  of  structures  in 
the  course  of  dissection  is  much  required  to  introduce  the 
student  to  more  complete  and  pretentious  records. 

A  tribute  of  respect  to  Professor  Pritchard  the  Author 
feels  to  be  a  duty ;  his  sound  anatomical  knowledge,  and 
his  skill  and  eloquence  in  communication  of  information  to 
those  who  have  the  pleasure  of  studying  under  him,  have 
indelibly  impressed  the  mind  of  the  Author  as  of  numerous 
other  members  of  the  veterinary  profession. 


The  Author  has  hoped,  therefore,  by  these  outlines  to 
introduce  the  student  of  veterinary  comparative  anatomy 
to  his  standard  of  comparison,  for  only  by  first  gain- 
ing a  knowledge  of  this  can  he  qualify  himself  for  the 
study.  In  the  dissecting  room  the  student's  investiga- 
tions are  in  the  first  place  confined  to  the  Eorse,  after- 
wards he  may  avail  himself  of  opportunities  of  ex- 
amining other  animals.  It  is,  therefore,  in  the  dissecting 
room,  during  this  first  stage  of  his  study,  this  work 
is  designed  to  render  him  assistance.  In  his  study  and 
at  his  leisure  he  will  fully  aj)i3reciate  the  beauties  and 
the  solid  value  of  the  works  above  alluded  to  ;  but  the 
student  in  the  dissecting  room  requires  conciseness,  a 
quality  which  the  Author  believes  he  has  been  successful  in 
harmonising  with  truth. 

And  if,  in  the  course  of  his  examination  of  Nahire,  th.e 
student  observes  errors  in  this  work  of  ari,  let  him  re- 
member "Varium  et  mutabile  semper  natura;"  let  him 
see  whether  he  has  not  discovered  one  of  those  exceptions 
which  but  serve  to  prove  Nature's  rules. 

A  work  of  this  kind  necessarily  omits  important  facts, 
but  the  author  has  endeavoured  to  insert  all  the  leading 
facts  of  his  subject,  almost  all  of  which  he  has  himself 
seen  in  the  dissecting  room.  When  obliged  to  trust  to  the 
observations  of  others,  he  has  referred  to  our  leading 
authorities ;  ho  has  not,  however,  hesitated  to  confirm  his 
own  observations  by  comparison  with  those  recorded  by 
others.  If  he  has  failed  in  supplying  to  veterinary  litera- 
ture a  work  of  which  he  himself  not  very  long  ago,  as  a 
student,  felt  the   need,  he  hopes  his  failure  will  stir  up 


PREFACE.  Vll 

some  abler  hand  to  the  work  ;  and  that  the  boldness  of 
this  attempt  will  be  pardoned  in  consideration  that  the 
aim  of  the  author  is  to  facilitate  the  acquisition  of  a 
knowledge  of  Veterinary  Anatomy,  and  thus  slightly  to 
serve  that  profession  to  which  it  is  at  once  his  pride  and 
his  honour  to  belong. 

J.  H.  S. 


Royal  Yet£ei>^aet  College, 
Nov.,  1S7C. 


OUTLINES 

OP 

EQUINE    ANATOMY, 


PART  I.— INTRODUCTORY. 

Anatomy  is  the  examination  by  means  of  dissection 
(cutting  up)  of  organized  bodies,  and  the  scientific  ar- 
rangement and  appreciation  of  the  parts  thus  separated 
with  regard  to  their  character  and  relative  position. 

The  science  of  anatomy  is  therefore  very  extensive ;  it  is 
primarily  divided  into  animal  and  vegetable  anatomy  ;  and 
animal  anatomy  is  called  Anthropotomy  when  man  is  the 
object  of  investigation,  Hippotomy  when  the  horse  is 
being  examined.  In  the  study  of  Comparative  Anatomy 
some  particular  species  of  animal  is  taken  as  the  standard, 
and  the  points  in  which  other  species  differ  from  this  are 
noted :  it  is  the  search  for  diversity.  Transcendental  or 
Philosophical  Anatomy  is  the  search  for  analogies  between 
different  species  and  the  endeavour  to  reduce  them  all  to 
a  general  type. 

Investigation  demonstrates  that  all  the  organs  of  the 
body  are  made  up  by  the  various  combinations  of  a  few 
primary  tissues  produced  by  union  of  anatomical  elements. 
The  study  of  these  tissues,  irrespective  of  their  situation, 
is  termed  General  Anatomy,  while  the  investigation  of 
their  component  elements  by  the  aid  of  the  microscope  is 
Histology. 

An  organ  of  the  body  is  a  collection  of  definitely 
arranged  tissues  for  the  performance  of  some  function  useful 


2  OUTLINES    OF    EQUINE    ANATOMY. 

to  the  animal  economy ;  the  lowest  forms  of  animal  life 
consist  of  but  one  organ,  a  simple  cell ;  but  in  ascending 
the  animal  scale  we  find  organ  after  organ  superadded, 
until  in  the  vertebrata  we  find  a  most  complex  collection 
of  mutually  dependent  organs  ;  the  study  of  the  characters 
and  relative  positions  of  these  and  the  arrangements  of  the 
tissues  of  which  they  are  composed  is  termed  Descriptive 
Anatomy. 

The  examination  of  healthy  organs  is  Physiological,  of 
diseased,  morbid  or  Pathological  Anatomy.  A  knowledge 
of  anatomy  enables  the  physician  to  diagnose  (distinguish) 
disease ;  the  surgeon  to  diagnose,  appreciate  the  extent  of, 
and  apply  the  best  means  of  remedy  for  injuries  and  mal- 
formations ;  and  the  natural  historian  to  arrange  the  various 
beings,  and  so  to  suggest  those  most  fit  for  economic 
purposes.  An  anatomist  only  can  duly  appreciate  the 
importance  of  the  ever  varying  points  constituting  "  un- 
soundness "  in  the  domesticated  animals. 

The  instruments  required  in  the  pursuit  of  descriptive 
anatomy  of  the  horse  are  not  numerous.  ScaJjoels  are  the 
agents  used  in  the  separation  of  the  soft  organs  one  from 
the  other,  a  firm  grasp  being  maintained  upon  the  most 
pliable  by  means  oi  forceps,  while,  if  necessary,  the  oppos- 
ing tissue  is  retained  in  position  by  hooks  and  chains.  The 
cutting  instruments  require  to  be  kept  sharp  by  means  of 
an  oil-stone.  In  some  cases  scissors  may  be  substituted  for 
scalpels  with  advantage,  as  in  clearing  arteries  and  in  dis- 
secting the  eye.  A  hloivjnpe  is  a  useful  accessory  for  the 
inflation  of  hollow  organs  with  thin  walls ;  a  saiv  is  abso- 
lutely necessary  for  the  proper  demonstration  of  the  various 
bony  cavities  and  of  the  structures  contained  in  them, 
while  a  chisel  and  hammer  serve  to  raise  the  separated 
portions  of  bone. 

The  vessels  require  to  be  filled  with  some  substance 
which  will  distend  them  as  they  naturally  exist  in  the 
livino-  animal,  and  thus  render  them  more  apparent. 
Arteries  and  veins  for  temporary  use  are  generally  dis- 
tended with  coloured  size  or  tallow,  which  solidify  as  the 
body  cools,  but  more  permanent  specimens  require  coloured 
wax";  mercury  is  useful  for  injecting  lymphatics.  The 
substance  is  forced  into  the  vessels  by  means  of  an  injecting 
syringe  which  has  stopcocJcs.  These  stopcocks  require  to 
be   introduced  into   the   large   arterial  trunks,  when  the 


INTRODUCTORY.  3 

material  will  fill  the  arteries  of  the  bodj,  but  the  valves 
of  the  veins  prevent  fluid  from  passing  from  their  larger  to 
their  smaller  branches,  so  it  is  here  necessary  to  com- 
mence at  the  smaller  vessels.  Lymphatics  are  injected 
by  introducing  the  point  of  the  syringe  into  the  areolar 
tissue  beside  the  arteries  and  veins  of  an  organ,  when 
the  mercury  will  generally  find  its  way  to  the  lym- 
phatics ;  they  are,  however,  but  seldom  dissected,  and 
being  valvular  like  the  veins,  cannot  be  injected  from  the 
larger  vessels. 

Solutions  of  nitric  and  other  acids  and  alcohol  are  used 
for  hardening  the  softer  organs,  as  the  brain  and  the 
eye,  while  by  maceration  or  boiling  the  bones  may  be 
cleaned,  and  thus  rendered  fit  for  demonstration  of  their 
peculiarities ;  by  boiling  also  we  render  apparent  the 
arrangement  of  the  muscular  fasciculi  of  the  heart.  The 
age  of  the  subject  influences  its  value  for  dissecting 
purposes.  Young  animals,  in  consequence  of  the  tender- 
ness of  their  areolar  tissue,  do  not  present  that  similarity 
between  bands  of  white  fibrous  tissue  and  the  nerves 
which  we  find  in  the  older  subject.  They  also  present 
well-marked  separations  between  the  bones,  and  in  many 
cases  the  various  ossific  centres  from  which  these  bones 
originate  ;  the  muscles,  though  more  easily  separable,  are 
less  marked  and  more  liable  to  tear  ;  an  older  subject  is, 
therefore,  preferable  for  dissection  of  muscles.  Fat  sub- 
jects are  said  to  keep  better  than  lean,  but  this  advantage 
is  more  than  counterbalanced  by  the  difficulty  of  removal 
of  the  adipose  tissue  from  some  parts.  Coarse  lymphatic 
animals  present  bulky  but  soft  muscles,  while  well-bred 
horses  and  asses  afford  firm  well-defined  muscles.  Since 
also  they  occupy  less  space  and  are  less  expensive,  asses  are 
generally  dissected  by  the  veterinary  student.  They  do 
not  difler  essentially  in  structure  from  the  horse.  The 
value  of  an  animal  for  dissection  may,  after  death,  be 
judged  by  taking  into  consideration  the  period  before 
accession  of  rigor  mortis  or  death  stiffening  and  the  length 
of  its  duration.  When  death  has  ensued  from  nervous 
prostration  the  vital  powers  soon  lose  their  control  over  the 
tissues.  Coagulation  of  the  albuminoid  matter  in  the 
muscles  occurs,  constituting  rigor  mortis,  but  soon  decom- 
position commences  as  a  result  of  the  substitution  of 
chemical  for  vital  force  in  the  tissues.     Such  a  subject, 


4  OUTLINES    OF    EQUINE    ANATOMY. 

therefore,  is  liable  to  decompose  sooner  than  one  of  oppo- 
site characteristics.  Human  bodies  are  preserved  by  injec- 
tion of  the  vessels  with  solution  of  arsenic,  carbolic  acid, 
and  other  preservative  fluids,  but  such  a  precaution  is  not 
necessary  in  veterinary  anatomy,  since  our  subjects  are 
destroyed  when  in  a  state  of  health,  are  cheaper,  and  will 
keep  for  three  weeks  with  care.  The  bodies  of  animals 
which  have  died  or  been  destroyed  when  suffering  from 
disease  are  deficient  in  tone  or  firmness  of  the  tissues  in 
general.  Death  from  hsemorrhage  or  bleeding  causes  a 
general  want  of  colour  of  the  parts,  and  therefore  of  one  of 
the  most  useful  guides  in  separation,  while  puncture  of 
the  brain  by  the  poleaxe  or  "  pithing "  produces  satis- 
factory results  with  instant  death. 

When  placed  on  the  dissecting-room  table  the  subject  is 
generally  rested  on  its  right  or  left  side  for  the  convenience 
of  the  dissectors,  six  of  whom  work  at  the  same  subject, 
dividing  it  among  themselves  into  six  parts — head,  neck, 
abdomen  (including  the  pelvis),  back  (including  the 
thorax),  fore  and  hind  extremities.  Such  a  division, 
though  extremely  artificial,  is  advantageous,  though  it 
requires  cordial  co-operation  at  the  boundaries  of  the 
various  regions  ;  thus,  the  longus  colli  lies  for  the  most 
part  in  the  neck,  but  extends  into  the  thorax  ;  the  proper 
demonstration  of  this  muscle,  therefore,  requires  the 
action  of  two  individuals.  The  subject  should  be  placed 
with  the  abdomen  towards  the  light,  as  the  organs  con- 
tained in  it  are  of  much  importance  and  require  careful 
dissection.  We  may  here  observe  that  some  art  is  re- 
quired in  the  distinction  of  the  different  structures  in 
different  positions  of  the  subject ;  diversity  in  this  respect, 
therefore,  while  it  renders  the  student  proficient  in  prac- 
tical anatomical  knowledge,  but  ill  accords  with  that 
"  cramming"  for  examination  which  consists  in  the  reten- 
tion verbatim  of  passages  from  books,  and  the  fixture  of 
pictures  of  the  subject  in  definite  positions  on  the  mind. 
The  pritnary  lines  of  incision  through  the  shin  are — 
I.  From  the  root  of  the  ear  to  the  throat  just  behind 

the  angle  of  the  jaw. 
n.  From  the  withers  to  the  point  of  the  shoulder  and 

on  to  the  centre  of  the  chest. 
III.  From  the  commencement  of  the  back  to  the  under 

surface  of  the  chest  near  the  elbow. 


INTRODUCTORY.  5 

IV.  From  the  posterior  part  of  the  loins  to  the  central 

line  of  the  abdomen  against  the  stifle. 
V.  From  the  centre  of  line  No.  Ill  to  the  centre  of 

line  No.  IV. 
VI.  Along  the  central  line  of  the  under  surface  of  the 

body  from  the  lower  lip  to  the  anus. 
In  making  these  incisions  care  must  be  taken  to  cut  the 
8kin  only,  for  under  it  in  some  places  important  structures 
are  superficially  situated.  The  skin  having  been  punc- 
tured by  a  slight  incision  at  first,  the  knife  (this  work  takes 
the  edge  off  an  ordinary  scalpel)  should  be  introduced, 
and  the  remainder  of  the  skin  divided  from  within  out- 
wards. From  the  primary  incisions  the  dissectors  then 
commence  to  separate  the  skin  from  the  neighbouring 
parts,  being  careful  to  cut  only  through  areolar  tissue,  the 
great  connecting  medium  of  the  other  tissues  ;  the  free 
flaps  in  a  short  time  produced  may  be  then  drawn  away 
from  the  subject,  whereby  the  areolar  tissue  is  rendered 
tense  and  thus  more  easily  perceptible  and  divisible.  Any 
blood  effused  by  accidental  or  intentional  incision  into 
veins  is  to  be  removed  with  a  sponge,  and  only  such  parts 
as  are  to  be  immediately  dissected  are  to  be  denuded  of 
skin,  for  on  exposure  the  areolar  tissue  becomes  dry  and 
tough,  assuming  the  appearance  of  dried  ligament  or 
tendon  in  some  places,  and  hence  becoming  liable  to  mis- 
lead. All  portions  of  separated  skin  should  be  imme- 
diately removed,  as  being  liable  to  cover  the  subject  with 
loose  hairs.'  The  bare  portions  may  be  kept  moist  by  damp 
cloths,  which  also  serve  to  keep  off  dust,  &c.  After  one 
side  of  the  animal  has  been  duly  investigated  much 
information  may  be  gained  by  turning  it  over  and  examin- 
ing the  other  side  by  a  similar  but  somewhat  modified 
process,  each  dissector  exchanging  his  region  for  some 
other,  whereby  the  most  satisfactory  amount  of  informa- 
tion gained  from  each  subject  by  each  individual  is 
attained. 

Finally,  we  will  recommend  that,  while  acquiring  that 
superficial  knowledge  of  the  situation  and  peculiarities  of 
the  bones  which  is  requisite  to  the  due  appreciation  of  the 
anatomical  position  of  organs,  the  student  avail  himself  of 
the  opportunity  of  learning  practically  the  handling  of  the 
scalpels,  skinning,  cleaning,  &c.,  for  the  first  subject  of  a 
student  generally  yields  him  hut  little  more  information  than 


6  OUTLINES    OP    EQUINE    ANATOMY. 

this.  Never  cut  througli  anytliiug  but  areolar  tissue  with- 
out having  examined  its  nature.  In  the  separation  of 
the  skin  the  edge  of  the  knife  must  be  always  turned 
towards  the  skin  from  the  unknown  tissues,  this  is  a 
primary  rule  in  dissection ;  always  cut  towards  known 
structures  when  dividing  areolar  tissue,  any  slip  of  the 
knife  will  then  do  no  damage. 

Where  possible,  have  the  basement  structure  of  the 
part,  as  the  bones  or  cartilages,  cleaned  to  show  its  points 
of  muscular  attachment,  &c.,  near  at  hand  for  constant 
reference,  and  during  dissection  take  advantage  of  the 
guidance  of  some  authentic  work  on  anatomy  read  aloud, 
or  better,  of  a  good  anatomist  \i\ 'propria  persona.  Care- 
fully note  any  point  in  which  the  subject  under  examina- 
tion differs  from  the  description. 

The  different  portions  of  the  subject  may  be  altered  in 
position,  irrespective  of  the  position  of  the  subject  in 
general,  by  means  of  hloclis  placed  under  parts  which 
require  to  be  elevated,  iron-forTced  bars  tirmly  fixed  in 
the  table  by  penetration  with  one  sharp  extremity,  which 
form  a  prop  for  limbs,  and  cords  either  from  pulleys  or 
from  fixed  points,  these  may  be  tightened  at  convenience. 

By  the  separation  of  organs  one  from  the  other  in  the 
dead  body  the  hand  and  the  eye  are  trained  for  operations 
upon  the  living  subject ;  the  student  therefore  should  not 
regret  the  time  expended  in  the  mechanical  pursuit  of 
anatomy,  nor  consider  that  examination  of  preparations, 
plates,  or  recent  specimens  prepared  by  others,  will  render 
him  proficient  in  anatomy  ;  it  is  only  men  who  work  on 
this  system  who  fear  the  ])ractical  anatomical  examination 
recommended  as  a  test  by  the  highest  authorities. 

One  of  the  most  prominent  characteristics  of  the  highest 
subkingdom  of  animals  is  the  possession  of  an  internal 
skeleton  or  basement  structure.  This  consists  of  a  number 
of  definitely  but  diversely  shaped  masses  of  a  hard  white 
substance  composed  of  a  mixture  of  earthy  and  animal 
matter.  Submit  a  bone  to  combustion  in  a  fire  with  a  free 
supply  of  air,  it  first  turns  black  in  consequence  of  the 
carbon  contained  in  its  animal  matter,  and  when  this  is 
completely  burnt  a  white  friable  mass,  in  shape  resem- 
bling the  bone,  remains,  being  the  earthy  matter  which 
entered  into  its  formation.  Subject  another  bone  to  the 
action  of  dilute  hydrochloric  acid,  this  will  remove  th<? 


INTRODUCTORY.  7 

earthy  matter,  and  tlie  animal  matter  will  remain  in  the 
shape  of  the  bone,  but  extremely  flexible. 

In  the  extremely  young  subject  all  the  bones  are 
cartilaginous,  being  elastic  and  pliable,  but  afterwards,  by 
the  deposit  of  earthy  matter  in  their  substance  and  by 
alteration  in  the  arrangement  of  their  component  ele- 
ments, they  change  to  bono.  This  process  of  ossifica- 
tion (bone  makings),  commencing  at  fixed  points,  involves 
gradually  the  surrounding  cartilage.  These  points  are 
termed  centres  of  ossification.  Some  cartilages  remain  of 
fixed  structure  throughout  life,  and  are  termed  "|jerma- 
7ient,^'  They  with  the  bones  therefore  form  the  skeleton, 
which  is  composed  of  many  portions  brought  into  mov- 
able contact  with  each  other,  whereby  the  various  motions 
of  the  body  are  possible  and  concussion  from  motion 
modified,  and  thus  shock  to  internal  organs  prevented. 
Where  firm  power  of  support  and  resistance  is  required 
bone  is  situated ;  where  yielding  with  protection  to  other 
parts,  cartilage.  When  these  structures  are  placed  in 
position  and  maintained  there  by  artificial  means  we  have 
an  artificial  skeleton,  but  in  the  natural  sheleton  they  are 
bound  together  by  bands  or  layers  of  a  strong  glistening 
fibrous  substance  (tvhite  fibrous  tissue)  or  of  a  yellow  elastic 
tissue,  the  characters  of  which  are  expressed  by  its  name. 
These  are  ligaments.  The  white  fibrous  tissue  under  the 
microscope  is  found  to  be  composed  of  collections  of 
parallel  bands  of  wavy  fibres  with  a  single  outline,  which 
bands  cross  each  other  irregularly.  Yellow  elastic  tissue 
consists  of  fibres  with  a  double  outline,  which  are  irregu- 
larly arranged,  but  send  branches  to  the  neighbouring 
fibres,  and  are  curled  at  their  extremities  in  consequence  of 
their  elastic  recoil. 

Cartilage  consists  essentially  of  cells  (circumscribed  sacs, 
each  containing  smaller  sacs  or  nuclei,  which  contain  a  cen- 
tral spot  or  nucleolus)  with  an  ijiter cellular  substance  or 
matrix.  In  the  true  or  hyaline  cartilage  this  matrix  is 
devoid  of  structure,  being  slightly  granular ;  but  when 
cartilage  requires  increased  strength  we  find  the  matrix 
assuming  the  characters  of  white  fibrous  tissue ;  where  it 
requires  elasticity,  yellow  elastic  tissue  ;  thus,  white  fibro- 
cartilage  and  yellow  elastic  fibro-cartilage  are  formed. 
These  three  forms  of  permanent  cartilage  present  cells 
collected  in  groups  of  about  three  or  four,  which  have  been 


8  OUTLINES   OF   EQUINE   ANATOMY. 

produced  by  division  of  one  cell,  but  tbe  cells  in  temporary 
cartilage  are  more  evenly  diffused  througb  the  mass. 
Another  form  of  cartilage  is  found  in  the  foetus,  which  is 
termed  cellular,  since  it  consists  of  cells  collected  together 
with  no  apparent  intercellular  substance. 

Bones  are  composed  of  compact  and  cancellated  structure. 
The  former  is  the  dense  external  layer  which  they  present. 
In  the  cancellated,  which  is  situated  more  internally,  the 
bony  structure  is  arranged  in  a  trabeculated  manner, 
whereby  spaces  are  left  which  are  termed  cancelli.  Small 
near  the  compact  substance,  these  gradually  increase  in 
size  until  in  the  centre  of  the  bone  we  frequently  find  a 
large  open  space  or  medullary  canal,  so  named  from  its 
containing  the  medulla  or  marrow,  a  greasy  substance, 
which  in  the  young  subject  is  of  a  red  colour,  but  in  the 
adult  yellow ;  it  consists  of  areolar  tissue,  in  the  meshes  of 
which  are  fat  and  peculiar  cells  (or  myeloplaxes)  ;  it  also  fills 
the  cancelli. 

The  intimate  structure  of  bones  is  complex ;  through  its 
substance  run  canals  for  blood-vessels,  and  arranged  con- 
centrically around  these  canals  are  bony  layers  termed 
lamince,  between  which  at  intervals  are  irregular  spaces 
containing  the  special  cells  of  bone,  or  lacunce.  From  each 
of  these  lacunae,  towards  the  central  or  Haversian  canal, 
and  towards  the  other  lacunae,  run  minute  passages  or 
canalicuU,  through  which  only  the  fluid  portion  or  nutritive 
plasma  of  the  blood  is  supposed  to  pass.  An  arrangement 
such  as  that  just  described  is  termed  an  Haversian  system, 
and  the  Haversian  canal  of  one  system  is  frequently 
brought  into  communication  with  that  of  another  by  means 
of  a  transverse  branch,  all  the  Haversian  systems  com- 
posing a  bone  are  not  uniform  in  size. 

Bones  are  of  three  kinds,  long,  flat,  and  irregular.  Long 
bones  (or  long  round  bones),  as  the  femur,  radius,  &c.,  have 
one  axis  (as  a  rule)  much  longer  than  the  others  and  have 
a  distinct  medullary  canal.  They  present  a  central  ossific 
centre  or  diaphysis  forming  the  body  of  the  bone,  and  at 
each  end  of  this  an  epiphysis  forming  an  extremity.  From 
either  part  processes  or  apophyses  may  j^roject.  Their 
Haversian  canals  run  parallel  to  the  long  axis  of  the  bone, 
and  the  different  Haversian  systems  are  connected  together 
by  connecting  laminae,  which  are  concentric  with  the  medul- 
lary canal  of  the  bone. 


INTRODUCTORY.  9 

Flat  bones  have  one  axis  mucli  shorter  than  the  others, 
whence  the  bone  assumes  an  expanded  form  and  serves  for 
the  attachment  of  large  muscles  or  for  forming  the  walls  of 
cavities.  They  present  no  medullary  canal,  but  between 
the  outer  compact  layers  is  cancellated  substance,  which  in 
the  cranial  bones  is  termed  diploe.  Examples  of  flat  bones 
— scapula,  parietal  bones.  They  have  a  centrally  situated 
centre  of  ossification,  with  others  for  their  processes,  and 
their  Haversian  canals  are  perpendicular  to  their  flat  sur- 
faces. Some  parts  of  them  seem  to  result  from  ossific 
deposit  in  fibrous  membrane,  and  not  from  change  of  car- 
tilage. 

Irregular  bones  are  those  in  which  no  marked  difference 
exists  between  the  length  of  their  axes.  They  consist  of 
cancellated  structure  surrounded  by  a  thin  layer  of  com- 
pact substance.  The  centres  of  ossification  are  related  to 
the  peculiarities  of  each  bone.  Examples— petrous,  temporal 
bones,  os  pedis,  &c.   In  this  class  are  included  "  short  hones." 

Bones  derive  their  supply  of  blood  from  the  arteries  which 
run  nearest  to  them ;  they  are  surrounded  by  a  strong 
membrane  composed  of  white  fibrous  tissue,  periosteum, 
which  is  very  vascular,  and  from  which  minute  vessels  pass 
to  foramina  on  the  surface  of  the  bone  in  connection  with 
the  Haversian  canals.  In  addition  to  this  long  bones 
generally  present  a  small  opening  {foramen  medullare), 
which  pierces  the  shaft  of  the  bone,  and  through  which 
passes  a  branch  from  the  nearest  important  artery  which 
runs  to  the  medullary  canal,  and  breaks  up  to  supply  the 
medulla  and  to  send  small  branches,  corresponding  with 
those  from  the  periosteum,  into  the  bone ;  and  a  third 
source  of  supply  is  derived  from  small  articulatory  foramina 
surrounding  those  surfaces  by  which  these  bones  come  into 
indirect  contact  with  each  other.  These  articulatory  sur- 
faces being  covered  with  cartilage,  are  not  covered  by 
periosteum,  which  also  is  absent  from  some  places  where 
tendons  become  directly  attached  to  the  bone,  and  from 
bones,  like  the  ethmoidal  cells  and  the  ossa  turbinata,  which 
are  intimately  clothed  with  highly  vascular  mucous  mem- 
brane. Bones  are  but  slightly  supplied  with  nerve- 
force,  their  lymphatics  have  not  been  satisfactorily  de- 
monstrated. Bones  present  eminences  and  cavities,  either 
of  which  may  be  articulatory  or  no n- articulatory. 


10 


OUTLINES    OF   EQUINE    ANATOMY. 


Articulatory         .  ^ 


Eminences  •{ 


I  Non-articulatory  < 


Articulatory 


^Seads. — Separated  from  main  por- 
tion of  bone  by  a  circumscribed 
neck,  being  rounded,  cf.  Head  of 
femur. 

Condyles. — Oval -rounded  projecting 
surfaces,    cf.  Condyles  ot  femur. 

Both  these  form  synovial  or  di- 
arthrodial  or  free-moving  joints  ; 
others  serve  to  form  fixed  or  im- 
perfectly movable  joints,  but  have 
no  definite  names. 
f  Imprints.  —  Rough,  irregular,  and 
small  prominences  for  attachment 
of  muscles,  tendons,  or  ligaments. 

Processes. — Lnrge  eminences  arising 
from  separate  centre  of  os^ifi(•atiou, 
variously  named  from  their  figures. 

Ridges     t  Eminences  with  elongated 

or  crests  j       bupis  of  attachment. 

Tuberosities. — Large  eminences  with 
l^     extremely  \^  ide  ba^e. 
r  Glenoid,  or  saucer-like,  shallow. 
'\  Cotyloid,  or  cup-like,  deep. 
{'Channels   or  furrows. — Wide,    deep, 
and  smooth. 

Grooves. — Long,  narrow,  and  even  at 
bottom. 

Fissures. — Narrow  and  rough. 

Digital  impressions. — Look  as  if  made 
by  the  finger  when  the  bones  were 
in  a  plastic  condition. 

FosscB. — Smooth  and  shallow. 
Non-articulatory  ^  Simises. — Cavities  divided  by  imper- 
fect septa  or  bony  partition. 

Notches. —  Grooves  scooped  at  the 
edge  of  a  bone. 

Foramina. — Cavities  passing  through 
bones. 

Canals. — Long  foramina. 

Fissures. — Narrow  torumina. 

Hiatus. — Wide  openings  with  irre- 
gular outlines. 

The  epiplijses  of  long  bones  consist  mainlv  of  cancellated 
tissue,  the  compact  portion  forming  but  a  thin  external 
layer ;  that  under  the  cartilage  (articular  laiimia)  is  most 
dense,  and  from  its  vessels  the  cartilage-cells  draw  nutriment. 
This  enlargement  of  the  extremities  of  the  bone  is  for  the 
purpose  of  affording  increased  surface  for  ligamentous  and 
other  attachments  without  increasing  the  weight  of  the  bone. 


Cavities  •{ 


INTRODUCTORY.  11 

For  convenience  of  description  anatomists,  wlien  possible, 
distinguish  surfaces  of  hones,  and  the  lines  of  union  of  the 
surfaces  constitute  the  borders. 

We  have  mentioned  ligaments  of  various  kinds  entering 
into  the  formation  or  perfection  of  joints.  These  are  gene- 
rally composed  mainly  of  white  fibrous  tissue ;  some  contain 
a  small  amount  of  yellow  elastic  tissue  ;  others  mainly  con- 
sist of  yellow  elastic  tissue,  as  ligamentum  nuchse.  We 
have  seen,  too,  that  the  ligaments  are  either  broad  expan- 
sions or  dense  bands.  Analogous  in  structure  are  the 
fascise,  which  are  found  in  particular  regions ;  they  con- 
sist of  widespread  membranous  layers  of  white  fibrous 
tissue,  which  form  sheaths  to  bind  down  muscles  in  their 
situations  and  to  brace  them  for  action  ;  they  are  generally 
attached  to  the  most  prominent  portions  of  the  basement 
structures  in  the  neighbourhood.  They  present  channels 
and  foramina  through  which  vessels  and  nerves  pass,  and 
in  some  cases  have  muscles  acting  upon  them,  as  tensor 
vaginae  femoris.  They  are  most  marked  in  those  situa- 
tions in  which  the  muscles  are  long,  as  in  the  limbs.  On 
approaching  an  annular  or  a  capsular  ligament  they  blend 
with  it.  The  most  important  are  fascia  lata  of  the  fore- 
arm, the  lumbar,  psoas,  and  gluteal  fascise,  and  the  fascia 
of  the  thigh.  The  gluteal  presents  a  considerable  amount 
of  yellow  elastic  tissue.  Fascia  superficialis  abdominis  is 
wholly  elastic.  The  several  portions  of  the  skeleton  are 
caused  to  move  upon  each  other  by  the  action  of  muscles. 
The  motion  found  in  other  parts  of  the  body,  with  the 
single  exception  of  that  produced  by  ciliae,  is  also  due  to  the 
peculiar  property  of  muscular  fibres  ;  this  motion  may  be 
voluntary  or  uncontrolled  hy  the  ivill,  and  is  brought  about 
by  the  contractility  of  two  forms  of  fibres,  voluntary  or 
striated,  involuntary  or  unstriated.  Involuntary  muscular 
fibre  is  that  which  produces  the  motion  of  most  of  the 
internal  organs  by  which  nutrition  and  reproduction  are 
brought  about ;  it  is  generally  arranged  so  as  to  form  a 
thin  coating  to  a  hollow  organ  or  a  tube  or  a  vesicle,  and 
consists  of  a  number  of  fusiform  or  spindle  shaped  nuclea- 
ted cells  overlapping  each  other  at  their  extremities  where 
they  meet.  The  double  wall  of  separation  becomes  ab- 
sorbed and  thus  a  plain  fibre  is  produced,  distended  at 
intervals  in  consequence  of  the  presence  of  the  nucleus; 
these  fibres  are  collected  together  to  form  fasciculi,  which 


12  OUTLINES    OF    EQUINE    ANATOMY. 

are  generally  spread  out,  forming  layers,  but  sometimes,  as 
in  the  large  intestine,  are  collected  to  form  bands.  When 
in  mass  they  are  white  in  colour.  Voluntary,  striated, 
or  red  muscular  fibre  is  that  which  is  under  the  control  of 
the  will  under  ordinary  circumstances.  It  consists  pri- 
marily of  certain  minute  globular  cells,  sarcous  elements, 
which  are  arranged  so  as  to  form  elongated  chains  or 
jibrillcB.  When  examined  under  any  but  the  highest 
powers  of  the  microscope  the  lines  of  junction  of  the  cells 
seem  like  black  lines  or  stri(B  extending  across  the  fibrillse. 
A  number  of  fibrillae  become  collected  into  a  bundle,  sur- 
rounded and  connected  together  by  a  layer  of  simple  mem- 
brane, the  sarcolemma,  to  form  a  fibre ;  and  the  fibres  are 
collected  into  fasciculi,  which  vary  in  size,  may  be  seen  with 
the  naked  eye,  and  are  surrounded  by  perimysium.  These 
fasciculi  are  united  together  to  form  masses  of  various 
shapes,  red  in  colour,  vulgarly  known  as  "flesh."  These 
are  the  muscles  of  anatomists  ;  the  study  of  them  consti- 
tutes myology.  Muscles  vary  much  in  form,  being  in  some 
cases  fusiform,  in  others  flat,  and  in  others  irregular  ;  they 
are  attached  to  the  basement  structures  in  most  cases,  and 
sometimes  consist  wholly  of  red  muscular  fibre,  in  others 
the  red  muscular  portion,  belly,  is  continued  by  a  white 
ligamentous  band,  which  may  be  cordiform,  or  expanded 
and  flat  (aponeurotic).  This  band  is  termed  a  tendon;  it 
consists  of  dense,  slightly  modified,  white  fibrous  tissue,  and 
in  some  places  becomes  firmly  blended  with  the  periosteum 
of  the  bones  to  which  it  runs,  in  others  becomes  continuous 
with  ligaments.  When  the  muscular  fibres  of  a  muscle 
meet  the  tendon  in  a  direction  obliquely  to  its  course  on 
one  side  the  muscle  is  termed  penniform ;  if  on  both  sides, 
hijpenniform ;  sometimes  two  fleshy  bellies  of  a  muscle  are 
connected  by  a  central  tendon,  such  a  muscle  is  said  to  be 
digastric.  Muscles,  as  a  rule,  cover  the  surfaces  of  bones 
and  form  grooves  and  channels  through  which  the  nerves 
and  blood-vessels  pass,  and  as  they  are  marked  more  or 
less  distinctly  in  different  cases  by  prominences  or  depres- 
sions on  the  surface  of  the  body  of  the  living  animal,  they 
afford  valuable  surs^ical  i^ruides.  Vessels  and  nerves  which 
run  in  contact  with  a  muscle  are  termed  its  satellites.  The 
muscles  are  extremely  numerous,  they  vary  in  size  from  the 
huge  longissimus  dorsi  to  the  minute  muscles  of  the  middle 
ear.      The  tendons   of   some  muscles  extend  throughout 


INTRODUCTORY.  13 

their  whole  length,  performing  the  function  of  a  ligament 
in  addition  to  their  motorial  value.  Muscles  are  gene- 
rally connected  together  by  areolar  tissue,  in  dissecting 
them  the  knife  should  be  always  used  in  the  direction  of 
their  fibres,  their  attachments  more  particularly  investi- 
gated, but  their  relations  and  figure  also  taken  into  account. 
Nerve-tissue  next  demands  notice,  as  being  the  source  of 
all  muscular  action,  sensation,  and  intellect.  The  nervous 
system  is  primarily  divided  into  the  cerebro-spinal  and 
sympathetic  systems,  each  of  which  consists  of  nerves  and 
nerve-centres  ;  the  two  are  intimately  blended.  The  cerebro- 
spinal nervous  system  is  that  which  regulates  animal 
life,  i.  e.  sensation,  voluntary  motion,  and  intellect.  Its 
centres  are  the  brainand  spinal  cord ;  its  nerves  are  marked 
by  whiteness,  they  are  given  off  from  the  above-mentioned 
centres,  as  a  rule,  in  pairs,  one  from  each  side  of  the  centre. 
Those  of  the  spinal  cord  originate  hy  two  sets  of  fibres,  a 
superior  or  sensory,  from  the  supero-lateral  part  of  the  cord ; 
each  of  these  has  a  ganglion  upon  it  and  subsequently 
unites  with  the  inferior  or  motor  root.  After  this  the  sen- 
sory cannot  be  distinguished  in  any  way  from  the  motor 
fibres  ;  the  difference  lies  not  in  the  fibres,  but  in  the  parts 
to  and  from  which  they  run.  The  sympathetic,  gang^lionic, 
or  vegetative  system  superintends  those  organs  which 
provide  directly  for  the  maintenance  of  the  individual  or 
the  perpetuation  of  the  species.  Its  centra  consist  of  a 
number  of  grey  nodular  bodies,  enlargements  of  the  nerves, 
found  in  various  parts  of  the  body  (termed  ganglia) .  Thus, 
they  exist  as  a  chain  of  ganglia  connected  together  by 
fibres  on  either  side  of  the  spine,  as  special  ganglia  existing 
in  certain  organs  as  the  heart,  as  the  ganglia  on  the  sensory 
roots  of  the  cerebro-spinal  nerves,  and  as  certain  ganglia 
situated  in  certain  irregular  but  constant  parts  of  the  body, 
as  those  of  the  fifth  cranial  nerve.  From  these  fibres  run, 
collected  into  nerves  distinguishable  by  their  darker  colour 
than  those  of  the  animal  system.  These  and  the  cerebro- 
spinal nerves  communicate  in  every  possible  manner. 
Two  classes  of  histological  elements  are  distinguishable  in 
nerve-tissue,  fibres  and  cells.  The  nerves  are  composed  only 
of  fibres  which  are  of  two  kinds,  grey  and  white.  The  grey 
fibres  so  much  resemble  unstriated  muscular  fibre  that 
their  nervous  nature  has  been  doubted.  They  are  found 
most  largely  in  the  sympathetic  nerves,  of  which  they  form 


14  OUTLINES    or   EQUINE   ANATOMY. 

the  greater  part,  and  consist  of  transparent  fibres  marked 
by  a  number  of  nuclei ;  they  are  smaller  in  calibre  and 
their  nuclei  more  crowded  than  those  of  unstriated  muscular 
fibre.  The  white  fibres  in  the  living  and  very  fresh  subject 
are  transparent,  resembling  extremely  minute  glass  threads, 
but  shortly  after  death  they  undergo  change  and  exhibit  a 
central  transparent  but  tough  substance,  axis  cylinder, 
surrounded  by  a  thin  layer  of  simple  membrane,  medullary 
sheath,  or  neurilemma,  while  between  the  two  is  a  quantity 
of  white  albuminoid  matter,  which  undergoes  coagulation, 
and  is  termed  the  ivhite  substance  of  Schivann.  These  fibres, 
with  a  few  grey  fibres,  are  united  together  to  form  those 
white  bands  commonly  known  as  nerves.  Some  of  them  seem 
to  commence  in  the  tissues  by  free  extremities,  others  by 
loops,  many  in  cells  which  will  be  found  most  marked 
in  the  organs  of  special  sense  and  in  voluntary  muscles. 
In  the  latter  we  find  these  cells  under  the  form  of  expanded 
plates  termed  the  motorial  'plates ;  the  rods  and  cones  of 
the  eye,  fibres  of  Corti  of  the  ear,  and  Pacinian  corpuscles 
of  the  skin,  are  cells  of  special  sense.  Nerve-cells  are  found 
in  the  nerve-centres,  they  are  sometimes  spheroidal,  but 
frequently  present  one,  two,  or  more  prolongations  from 
which  the  axis  cylinders  of  the  nerves  pass.  They  are 
termed  polar  cells  {multi-,  hi-,  according  to  whether  they 
have  many  or  but  two  prolongations).  They  abound  in 
the  grey  portions  of  the  centres,  the  white  being  mainly 
composed  of  nerve-fibres,  connective  tissue,  and  granular 
matter.  Nerve-cells  present  each  a  nucleus  with  one  or 
more  nucleoli  surrounded  by  granular  matter  sometimes  of 
a  dark  colour.* 

We  have  seen  examples  of  pure  membrane  or  lemma  in 
the  investing  layers  of  the  nerve  and  muscular  elements 
termed  respectively  neurilemma  and  sarcolemma.  A  third 
form  is  brought  under  our  notice  in  investigating  the  com- 
plex membranes  of  the  body.  It  is  termed  basement  mem- 
brane, and  consists  of  a  thin  structureless  or  slightly 
granular  fibre  on  one  side  in  contact  with  connective  tissue 
with  numerous  vessels,  on  the  other  with  cells  with  more 
or  less  marked  walls,  nuclei,  and  nucleoli,  termed  epithelial 

*  When  a  number  of  nerves  passing  from  different  parts  of  a  centre 
become  mixed  at  one  part,  and  from  this  nerves,  each  composed  of 
fibres  from  several  parts  uf  the  centre,  run  to  distinct  organs,  we  term 
the  arrangement  a  plexus. 


INTRODUCTORY.  15 

cells.  The  compound  membranes  are  together  made  up 
therefore  of  internally  a  vasculo-areolar  layer,  centrally 
basement  membrane,  externally  epithelial  cells.  They 
are  of  four  kinds — serous,  synovial,  mucous,  and  cuticular. 

Serous  membranes  are  the  most  simple.  They  line 
closed  sacs,  do  not  secrete  fluid  from  the  blood,  but  merely 
are  moistened  by  some  halitus  or  vapour  which  serves  to 
allow  them  to  move  freely  upon  each  other  without  friction, 
for  two  layers  of  serous  membrane  generally  come  in 
contact  whereby  motion  of  the  contents  of  a  cavity  without 
motion  of  its  walls  is  admissible.  The  epithelium  of  this 
form  of  membrane  consists  of  a  single  layer  of  cells  spread 
over  the  surface  of  the  basement  membrane,  closely  fitted 
together,  whereby  each  assumes  the  hexagonal  form  charac- 
teristic of  tessellated  epithelimn.  The  pleura,  pericardium, 
and  arachnoid  are  good  examples  of  serous  membranes.  It 
is  supposed  that  they  are  merely  dilated  extremities  of 
lymphatics.  Synovial  membranes  differ  from  serous  in  their 
greater  complexity  and  in  the  nature  of  their  secretion,  for 
they  separate  from  the  blood  a  fluid  which,  in  consequence 
of  the  fatty  matter  it  contains,  serves  to  lubricate  freely  mov- 
able joints.  They  therefore  line  the  cavities  of  such  joints 
covering  the  inner  surface  of  its  ligaments,  and  in  young 
animals  even  extending  over  the  cartilage  of  the  articular 
surfaces  of  the  bones.  In  some  parts,  either  to  fill  up  space 
or  to  afford  increased  secreting  surface,  the  vascular  layer 
of  the  membrane  is  thickened,  rendering  it  prominent  and 
heightened  in  colour,  forming  the  synovial  fring'es.  Besides 
lining  the  cavities  of  joints  synovial  membranes  form  the 
thecae  or  sheaths  of  tendons,  lining  the  channels  through 
which  they  pass,  and  being  reflected  over  the  tendons,the  two 
portions  being  connected  by  double  folds  of  membrane 
termed /roe?^a.  Whenever  a  tendon  plays  over  a  prominent 
surface  whereby  the  direction  of  its  action  is  altered  it  has 
placed  between  it  and  the  prominence  a  small  synovial 
closed  sac  termed  a  bursa,  the  third  form  of  synovial  cavity  ; 
a  marked  bursa  is  situated  between  extensor  pedis  tendon 
and  the  antero-inferior  part  of  metacarpi  magnum,  the 
synovial  apparatus  between  flexor  brachii  and  the  humerus 
is  intermediate  in  character  between  a  theca  and  a  bursa. 
Sometimes  two  or  even  three  of  the  different  forms  of 
synovial  cavity  communicate.  Synovial  membranes  always 
present  simple  tessellated  epithelium.     It  is  on  the  Mucous 


16  OUTLINES    OF    EqUINE    ANATOMY. 

membranes  that  we  find  it  gaining  its  greatest  complexity, 
in  some  cases  consisting  of  several  superimposed  layers,  the 
most  internal  of  which,  drawing  nutriment  from  the  blood, 
''hands  it  on"  to  those  more  externally  placed.     This  is 
stratified   epithelium.     In  some  cases,  however,  as  in   the 
guttural  pouch,  we  find  the  mucous  membrane  resembling 
a  serous    membrane  in  the    simplicity  of   its  component 
elements.     The  vascular   layer   of   mucous   membrane  is 
termed  corium,  and  is  sometimes  thick,  presenting  numerous 
and  large  blood-vessels,  as  in  the  case  of  the  mucous  mem- 
.  brane  of  the  hard  palate.     In  some  situations  it  is  extremely 
attenuated  or  even,  as  in  the  corneal  conjuctiva,  completely 
absent.     Epithelium  of  mucous  membrane  is  of  two  kinds, 
ciliated  or  non-ciliated.     Non-ciliated  epithelium  may  be 
either  tessellated  (above  described)  or,  the  mutual  compres- 
sion of  the  cells  not  being  so  great,  they  may  retain  the 
spheroidal  figure  (as  in  the  bladder,  ureters,  and  pelvis  of 
the  kidney) ,  or  the  cells  may  be  cylindrical,  fitting  in  closely 
together,  having  one  extremity  free,  the  other  in  contact 
with  the  basement  membrane.      This  is  columnar  epithe- 
lium ;  it  lines  the   greater  portion  of  the  digestive  tract. 
Either  columnar  or  spheroidal  cells  may  present  on  their 
free  surface  a    number    of   small   pointed   prolongations 
which,  by  some  peculiar  power  independent  of  nerve  in- 
fluence, wave  to  and  fro.     These  are  ciliae,  their  presence 
is  manifest  in  the  respiratory  tract,  where  their  action  serves 
to  waft  upwards  mucus  for  expectoratiou  ;  and  also  in  the 
Fallopian  tube,  where  they  waft  the  sperm- cell  upwards, 
the  germ-cell  downwards.      Mucous  membrane  lines   all 
those  great  cavities  of  the  body  which  communicate  with  the 
external  air,  but  the  distinction  hetween  the  mucous  and  serous 
membranes  is  very  artificial.     Thus,  the  alimentary,  respira- 
tory, genito-uriimry  and  lachrymal  tracts  are  all  lined  by 
mucous  membrane,  and  as  this  insensibly  blends  with  the 
skin  at  the  external  openings  of  the  body,  we  may  look 
upon  the  structures  of  the  body  already  described  as  con- 
tained in  a  large  sac  of  compound  membrane.     In  some 
parts  the  corium  of  mucous  membranes  presents  unstriated 
muscular  fibre,  in  others  it  is  thickened  at  certain  points 
producing  papillce,  such    as   those  found   on  the  tongue 
and  the  intestinal  mucous  membrane.     Other  peculiarities 
in  the  mucous  membranes  will  be  noticed  in  the  descrip- 
tions of  different  parts ;  thus,  the  teeth,  as  will  be  shown, 


INTRODUCTORY. 


17 


are  modified  mucous  memhrane.  The  skin  consists  of 
exactly  the  same  component  elements  as  other  membranes, 
but  they  are  generally  more  complex.  It  is  in  many 
parts  continuous  with  the  larger  mucous  membrane,  and 
all  over  its  surface  presents  openings  leading  into  glands. 
It  presents  modifications  under  the  form  of  hair  and  hoof. 
It  consists  of  two  parts  separated  by  basement  membrane, 
dermis  and  ejiidermis.  The  dermis  corresponds  to  the 
corium  of  mucous  membrane,  and  consists  of  a  more  or 
less  thick  layer  of  reticulated  yellow  elastic  and  white 
fibres,  containing  in  their  meshes  vessels  and  nerves.  It 
presents  two  layers,  the  reticulated  and  papillated.  The 
reticulated  layer  internally  situated,  its  deep-seated  surface 
is  continuous  with  the  subcutaneous  areolar  tissue,  its 
superficial  with  the  papillated  layer,  which  is  externally 
raised  into  a  number  of  finger-like  prominences  (covered 
with  basement  membrane),  on  to  which  the  epidermis  is 
moulded.  The  subcutaneous  areolar  tissue  varies  in  its 
density  in  different  parts  of  the  body,  being  in  some  places 
very  loose,  as  in  the  intermaxillary  space,  on  the  chest,  &c. 
These  parts  are  most  liable  to  dropsical  collections  and 
most  readily  admit  insertion  of  setons.  It  contains  col- 
lections of  fat,  the  terminations  of  the  hair-follicles  and  of 
the  sudoriparous  glands.  Portions  of  these  also,  and  the 
sebaceous  glands,  are  embedded  in  the  dermis.  The 
epidermis  consists  of  epithelial  cells  moulded  upon  the 
external  surface  of  the  dermis ;  the  most  deep-seated  are 
spheroidal  and  contain  pigment-granules,  forming  the  rete 
mucosum.  The  superficial  layers  become  hard,  dry,  and 
scaly  ;  as  they  are  subjected  to  external  influences,  they  are 
gradually  worn  away. 

Hairs  are  produced  from  depressions  on  the  surface  of 
the  skin  termed  hair-follicles.  These  are  filled  with 
spheroidal  epithelium,  and  into  each  of  them  open  gene- 
rally the  ducts  of  two  sebaceous  glands.  At  its  deep- 
seated  extremity,  where  it  forms  a  cul-de-sac,  each  follicle 
presents  a  papilla  from  which  the  hair  is  produced.  The 
hair  is  the  epithelium  of  the  papilla  (which  is  of  the  same 
nature  as  the  dermis).  It  consists  of  a  hulh,  apex,  and 
shaft.  The  hulb  immediately  surmounts  the  papilla,  and 
is  the  largest  portion  of  the  hair,  consisting  of  the  softest 
and  most  recently  formed  spheroidal  cells.  The  shaft  is 
the  cylindrical  portion  which  runs  outwards,  emerges  from 


18  OUTLINES    or    EQUINE   ANATOMY. 

the  follicle,  and  terminates  in  the  apsx.  It  consists  of  an 
external  or  cortical  layer,  the  cells  of  which  are  imbricated 
(arranged  like  tiles  upon  a  honse),  and  a  central  medul- 
lary portion,  consisting  of  soft,  spheroidal  cells.  The 
sebaceous  glands  pour  their  secretion  into  the  follicle  ;  it 
is  an  oily  substance,  and  permeates  the  hair,  rendering  it 
pliable.  These  glands  are  small  fiask-shaped  bodies  of  the 
racemose  class.  The  sudoriparous  glands  produce  the 
sudor  or  sweat,  which  thej  pour  out  upon  the  surface  of 
the  skin.  Each  gland  consists  of  a  single  elongated  tube, 
which  is  ver  J  much  twisted  upon  itself  in  the  subcutaneous 
areolar  tissue  so  as  to  form  a  small,  rounded  mass  per- 
meated by  blood-vessels.  It  takes  a  slightly  wavy  course 
through  the  dermis,  and  in  passing  through  the  epidermis 
becomes  cork-screw  like.  Hairs  are  either  short  and  glossy, 
as  those  covering  the  surface  of  the  body  in  general,  or 
long  and  coarse,  with  their  bulbs  deeply  imbedded  in  the 
subcutaneous  tissue,  forming  horsehair,  found  in  the  mane, 
tajl,  eyebrows,  eyelashes,  and  tentaculse  of  the  lips,  which 
in  the  upper  lip  of  some  coarse-bred  horses  become  long 
and  wavy  like  the  human  mustachois.  Fineness  and 
scantiness  of  hair  is  a  mark  of  a  well-bred  horse.  It  varies 
in  colour  in  horses  from  white  to  black.  In  the  ass  it  gene- 
rally assumes  a  brownish-white  mouse  colour,  and  a  dark 
line  of  hair  extending  down  the  back  assists  in  distin- 
guishing Equus  asinus  from  E.  caballus.  The  modifica- 
tion which  hair  undergoes  in  forming  horn  will  be 
described  in  its  proper  place. 

We  must  now  examine  those  complex  arrangements  of 
mucous  membrane  which  produce  glands.  All  glands  are 
depressions  in  mucous  membrane,  and  these  depressions 
may  assume  either  the  tubular  or  the  follicular  form,  and 
either  of  these  may  be  simple  or  compound.  Simple  tubu- 
lar glands  are  those  which  consist  of  a  single  undivided 
tubular  depression  of  mucous  membrane  :  examples  are  the 
follicles  of  Lieberkiihn,  and  the  sudoriparous  glands — the 
former  of  which  are  extremely  shallow,  the  latter  much 
elongated.  Sometimes  these  tubes  divide  at  their  deep- 
seated  extremities,  and  each  part  may  again  subdivide,  and 
thus,  by  continuation  of  this  process,  compound  tubular 
glands,  such  as  the  testes  or  the  kidneys,  are  produced ; 
the  latter  organ  has  dilated  extremities  of  its  tubules,  and 
thus  resembles  compound  follicular  glands. 


INTRODUCTORY.  19 

Simple  follicular  glands  are  flask-shaped  bodies  openini,^ 
on  to  the  surface  bj  a  small  duct ;  when  several  of  these 
pour  their  secretion  into  a  compound  duct,  we  see  the  first 
example  of  a  compound  follicular  or  racemose  gland, 
which  consists  of  a  number  of  flask-shaped  or  vesicular 
bodies,  which  pour  their  secretions  through  a  number  of 
ducts,  which  unite  and  reunite  until  at  last  thej  form  a 
more  or  less  elongated  canal,  the  duct  of  the  gland,  which 
opens  on  to  the  surface  of  the  mucous  membrane  lining 
the  cavity  to  which  the  gland  is  appended.  The  secreting 
vesicles  or  acini  thus  bear  to  the  ducts  the  relation  which 
grapes  bear  to  their  stalks,  hence  the  name  racemose. 
The  several  parts  of  the  gland  are  closely  invested  by 
areolar  tissue,  whereby  they  are  united  to  form  lobules, 
which  by  their  union  complete  the  gland.  As  examples  of 
compound  follicular  glands,  may  be  adduced  the  salivary, 
pancreas,  lachrymal,  and  mammary  glands,  while  the 
meibomian,  brunners,  and  the  sebaceous  glands  present 
this  type  under  a  much  less  complex  form. 

The  so-called  ductless  glands  present  peculiar  charac- 
ters, which  will  be  specially  noticed.  All  the  above- 
mentioned  structures  are  supplied  with  matter  for  growth 
and  for  rej)air  by  the  blood,  and  the  same  fluid  also  re- 
moves matters  for  which  they  have  no  longer  use.  It  is 
conveyed  from  the  heart  throughout  the  system  by  cer- 
tain vessels  found  in  all  parts  of  the  body  more  or  less. 
It  must,  however,  be  clearly  understood  that  in  all  cases 
the  special  cells  of  a  tissue  are  externally  placed  to  the 
blood-vessels,  so  that  all  nutriment  obtained  by  any  but 
blood-cells  must  be  obtained  through  the  walls  of  the 
vessels  and  through  the  wall  of  the  cell.  The  vascularity 
of  a  part  consists  in  the  close  relation  of  its  cells  to  its 
vessels.  Thus  the  capillaries  run  between  the  muscular 
fibrillae  of  voluntary  muscle  ;  they  are  separated  from  the 
cells  by  basement  membrane  in  the  complex  membranes  ; 
in  stratified  epithelium  the  outer  layers  are  separated  by 
basement  membrane  and  a  number  of  cells  which  hand  on 
the  nutritive  portion  or  plasma  of  the  blood  from  within 
outwards.  The  same  condition  obtains  in  cartilage  except 
that  the  cells  are  separated  by  intercellular  substance  of 
variable  nature  and  amount ;  while  in  bone  the  plasma 
passes  through  an  elongated  but  extremely  minute  canal 
m  its  course  from  the  vessel  to  the  cell.     The  vessels  from 


20  OUTLINES    OP    EQUINE    ANATOMY. 

whicli  the  cells  directly  derive  the  plasma  are  the  capil- 
laries, extremely  minute  vessels,  uniform  in  size,  forming 
an  intricate  network,  varying  in  the  figure  of  its  inter- 
spaces in  the  different  tissues,  which  in  muscle  are  elon- 
gated parallelograms,  in  lungs  smaller  than  the  vessels 
themselves.  These  vessels  connect  the  terminal  extremi- 
ties of  the  arteries  with  the  commencement  twigs  of  the 
veins  ;  the  blood  does  not  take  any  definite  course 
through  them.  The  wall  of  the  capillary  consists  of 
simple  membrane  with  more  or  less  numerous  nuclei 
imbedded  in  its  substance.  When  the  vessels  are  large 
they  present  nuclei  elongated  both  longitudinally  and 
transversely  ;  the  smaller  vessels  have  only  longitudinal 
nuclei,  which  are  widely  scattered.  The  brain  and  the 
mucous  membrane  of  the  bowels  present  extremely  minute 
capillaries,  those  of  the  skin  are  very  large  (as  may  be 
well  seen  in  that  part  modified  to  form  the  hoof) .  In  the 
spleen,  corpus  cavernosum  penis,  and  in  the  chorion,  the 
arteries  open  directly  into  veins  usually  modified  to  form 
venous  sinuses. 

The  arteries  carry  blood  from  the  heart  to  the  tissues. 
They  vary  in  size  in  proportion  to  their  distance  from  the 
heart.  They  may  be  distinguished  from  the  veins  by 
their  elasticity,  which  enables  them  to  remain  open  after 
death,  and  also  to  expel  the  blood  which  they  contained 
when  the  heart's  action  ceased,  whence  they  are  found 
empty.  The  sum  of  the  areas  of  the  arteries  at  a  distance 
from  the  heart  is  greater  than  the  area  of  the  aorta,  and 
the  size  of  this  sum  is  great  in  proportion  to  the  distance 
from  the  heart,  so  that  the  arterial  system  has  fancifully 
been  described  as  a  cone,  the  apex  of  which  is  at  the 
aorta,  the  base  at  the  capillaries,  in  which  the  smallest 
arteries  terminate.  Arteries  may  be  given  off  at  right 
angles  or  at  an  acute  angle  from  a  large  trunk ;  as  the 
pressure  of  fluids  in  closed  vessels  is  equal  in  all  directions, 
this  arrangement  will  scarcely  influence  the  flow  of  blood  to 
particular  parts.  Some  arteries  run  directly  to  the  organs 
which  they  supply,  others,  especially  the  spermatic  artery 
in  the  horse,  assume  a  peculiar  convoluted  character ; 
while  in  some  cases  several  vessels  unite  to  form  a  more 
or  less  intricate  plexus  termed  rete  mirabile,  examples  of 
which  may  be  seen  in  the  circle  of  Willis  and  the  circular 
arteriosus  of  the  foot.     Arteries  possess  three  coats.     The 


INTRODUCTORY. 


21 


external  or  fihro -areolar  coat  consists  of  more  or  less  con- 
densed areolar  tissue,  with  a  slight  predominance  of  elastic 
fibres  ;  it  serves  to  protect  the  vessels  and    to  form  the 
nidus  in  which  the  small  nutrient  vessels  of  the  arterial 
coats   (vasa  vasorum)    break    up   into    capillaries.     It   is 
directly  continuous  with  the  areolar  tissue  of  the  channel 
through  which  the  artery  runs,  which  sometimes  becomes 
developed  into  a  marked  sheath  enclosing  other  structures 
in  addition  to  the  artery  ;  the  carotid  sheath  is  an  example. 
The  middle  or  musculo -elastic  coat  consists  of  unstriated 
muscular  fibre  in  union  with  yellow  elastic  tissue.     The 
muscular  fibres  assume  a  direction  transverse  to  the  longi- 
tudinal axis  of  the  vessel ;  they  predominate  in  the  smallest 
arteries,  those  most  distant  from  the  heart.     The  elastic 
fibres     mainly    take    a    longitudinal    direction,    but    are 
arranged  in  the  form  of  a  network  ;  in  the  largest  arteries, 
as  the  aorta,  they  form  the  major  portion  of  the  arterial 
wall.     The  internal  coat  is  of  a  serous  nature,  presenting 
an  internal  layer  of  tessellated  epithelium  and  a  peculiarly 
modified  basement  membrane.     The  latter,  termed  the  fenes- 
trated membrane  of  Henle,  shows  a  peculiar  tendency  to 
curl  up  when  removed  from    its    situation,  and   it   has 
numerous  perforations.     These  characters  seem  to  indi- 
cate its  intermediate  nature  between  common  basement 
membrane    and    ordinary     yellow     elastic     tissue    with 
which  in  some  vessels  its  external  surface  intimately  blends. 
This  coat  of  the  artery   is  continuous  centrally  with  the 
endocardium,  peripherally  with  the  constituent  membrane 
of  the  capillaries.     The  course  of  arteries  is  in  some  cases 
irregular,  either  as    a    result    of    disease  or    of   original 
formation.     Descriptions  of  these  cannot  be  accurate /or 
all   cases.      When    arteries    run    near    one  another  they 
almost    always    anastomose    or    inosculate,    communicate 
more    or    less   closely,    either    directly    or    by    branches. 
Hence  provision  is  made    for    continuance  of  supply   of 
blood  after  obliteration  of  one  source  ;  the  collateral  sources 
after  injury  resulting    in    obliteration    of    an    important 
artery  generally  prove  equal  to  the  emergency— a  point  of 
great  value  in  surgery. 

The  veins  carry  blood  from  the  capillaries  to  the  heart 
with  exception  of  the  portal  veins,  which  convey  it  from 
the  alimentary  organs  of  the  abdomen  to  the  liver,  where  it 
is  purified  prior  to  admission  into  the  general  round  of 


2^  OUTLINES    OF    EQUJNE    ANATOMY. 

the  circulation.  Arteries  inosculate  or  anastomose  in  some 
situations  freely,  but  veins  rarely  approach  each  other 
without  communication  ;  they  are  also  more  numerouSj 
much  less  regular,  and  larger  than  arteries.  A  portion  of 
vein  removed  from  the  body  will  be  found  more  or  less 
coloured  by  blood  which  has  remained  in  it  after  death. 
The  thinness  of  its  walls  will  allow  it  to  collapse  when 
placed  upon  a  flat  surface.  Like  arteries  veins  have  three 
coats,  which  differ  from  those  of  the  arteries  in  the  paucity 
of  their  component  elements.  The  internal  or  seroid  coat, 
however,  requires  notice,  for,  in  addition  to  lining  the 
vessel,  it  projects  into  the  cavity,  double  folds  constituting 
valves  of  a  semilunar  form.  These  always  have  their  free 
margins  and  concave  surfaces  directed  towards  the  heart, 
for  they  perform  an  important  function  in  promoting  the 
circulation.  According  to  the  size  of  the  vessel  from  one 
to  three  valves  may  coexist  at  one  particular  part.  Only 
two  arteries,  aorta  and  pulmonary  artery,  possess  valves, 
and  they  look  from  the  heart.  Some  veins,  as  those  of  the 
foot,  portal  system,  and  several  components  of  the  ante- 
rior and  posterior  venae  cavse,  have  no  valves ;  in  other 
situations  the  valves  are  few  in  number.  When  not  in  use 
during  the  forcible  rush  of  blood  through  the  vessels,  the 
valves  lie  against  the  sides  of  the  vessel.  This  is  their  ordi- 
nary situation  in  the  jugulars,  in  which  they  come  into 
action  only  when  the  animal's  head  is  lowered,  as  in 
grazing  ;  under  other  circumstances  the  blood  passes  to  the 
heart  in  virtue  of  its  own  weight.  Certain  modifications 
of  veins,  termed  venous  simises,  will  be  noticed  in  due 
course. 

In  addition  to  blood-vessels  we  find  other  vessels  which 
convey  a  fluid  from  which  blood  is  prepared.  The  free 
spaces  of  the  body,  and,  according  to  some  authorities, 
even  the  serous  cavities,  are  lined  by  an  epithelial  mem- 
brane, continuous  with  that  lining  certain  vessels  termed 
lymphatics,  which  unite  and  reunite  until  at  length  they 
pour  their  contents  into  the  blood-vessels.  These  vessels 
probably  run  from  all  parts  of  the  body  ;  the  largest  trunks 
which  they  form  are  the  tJioracic  duct  and  the  great  right 
lymphatic,  which  open  into  the  large  veins  at  the  anterior 
part  of  the  chest.  The  smallest  lymphatics  resemble 
the  capillaries  in  structure,  the  largest  closely  resemble 
veins,  presenting  valves,  and  passing  towards  the  centre  of 


INTRODUCTORY.  23 

circulation,  but  they  anastomose  less  freely,  tlieir  valves 
are  less  numerous,  the  fluid  they  contain  is  colourless,  and 
sooner  or  later  almost  all  of  them  pass  through  certain 
dark  grey  nodular  bodies,  found  in  various  parts  of 
the  body,  termed  lymphatic  glands.  These  produce  a 
change  in  the  nature  of  the  contained  fluid,  and  seem  to 
be  mere  means  of  economy  of  space,  since  some  of  the 
lower  animals  in  place  of  glands  present  extreme  elonga- 
tion and  tortuosity  of  the  lymph  vessels.  In  these  lower 
aniniEfels  the  lymph  vessels  present  in  some  parts  dilata- 
tions with  thick  muscular  walls,  lymph  hearts,  which 
drive  the  lymph  into  the  blood-vascular  system  in  several 
situations.  In  the  higher  vertebrata  the  communication 
between  the  blood  and  lymph  systems  seems  to  occur  only 
at  the  anterior  part  of  the  thorax.  Some  authorities  have 
described  these  large  lymph  vessels  as  contractile. 

Lymphatic  glands  consist  of  a  special  investing  coat 
with  trabeculse  passing  inwards,  dividing  the  contained 
space  into  cavities,  of  which  the  external  are  most  marked, 
all  of  which  are  lined  with  epithelium.  The  external  por- 
tion, therefore,  is  softest,  and  is  termed  the  cortical  portion  ; 
the  firmer  central  structure  is  the  medullary  structure.  A 
number  of  beaded  afferent  lymphatics  converge  and  pass 
into  a  gland  ;  they  seem  primarily  to  pass  to  the  medullary 
portion  in  which  they  are  arranged  in  a  convoluted  mass. 
They  are  supposed  to  open  into  the  cavities  of  the  gland, 
lymph  spaces,  and  the  lymph  to  pass  irregularly  through 
these  until  it  arrives  at  the  commencement  portion  of  the 
efferent  lymphatics,  which,  larger  and  less  numerous  than 
the  afferent  vessels,  on  emerging  from  the  gland  pass 
towards  the  main  lymphatic  trunks. 

The  lymph  vessels  of  the  bowels  are  distinctively  called 
the  lacteals,  for  the  fluid  they  convey  is  rendered  opaque 
and  milky  in  appearance  by  the  presence  of  fatty  globules 
taken  up  from  the  contents  of  the  intestines  by  these 
vessels.  They  differ  in  no  respect  from  other  lymphatics  ; 
th,ey  commence  in  the  villi  of  the  intestines  either  in  blind 
extremities,  in  loops,  or  in  plexuses. 


21*  OUTLINES    OF    EQUINE    ANATOM^ 


PART  II— OSTEOLOGY. 


THE  SKULL, 

with  a  few  cartilaginous  accessory  structures,  forras  tlie 
basement  structure  of  the  head.  It  is  composed  of  modi- 
fied vertebrae,  united  together  in  such  a  manner  as  to  form 
numerous  cavities,  mostly  for  the  purpose  of  protecting 
important  organs.  It  is  a  conical  body,  the  apex  part  or 
muzzle,  of  which  we  shall  consider  as  being  directed  for- 
wards, the  base  towards  the  trunk  to  which  it  is  united  by 
the  neck.  It  is  divided  into  the  cranium,  which  corre- 
sponds to  the  neural  portion  of  the  other  vertebrae,  and  the 
face,  which  is  antero-inferiorly  placed,  and  corresponds  to 
the  haemal  ring.     The  latter  much  predominates  in  size. 

THE  CRANIITM 

consists  of  twelve  bones,  four  pairs  and  four  single.  The 
cavity  formed  by  these  bones  will  be  considered  when  its 
contents  are  to  be  examined ;  we  shall  here  examine  as 
distinct  bones  those  osseous  masses  which,  in  the  adult, 
are  firmly  united  into  a  single  mass  with  those  of  the  face 
forming  the  upper  jaw.  The  lower  jaw  is  formed  by  a 
special  bone  of  the  face  (the  inferior  maxillary  bone). 
The  union  between  the  upper  and  lower  jaws,  and  that 
])etween  the  cranium  and  the  first  cervical  vertebra,  are 
the  only  examples  of  synovial  articulations  to  be  found 
in  the  skull.  The  union  of  os  hyoides  (the  tongue  bone) 
with  the  base  of  the  skull  is  fibro-cartilaginous.  All  the 
other  joints  are  immoveable,  and  sooner  or  later  become 
obliterated. 

OS  OCCIPITIS  is  the  postero- superior  bone  of  the 
cranium,  that  which  articulates  with  the  atlas,  and  which 
forms  the  "poll."  It  is  divided  into  hody, condyles,  basilar 
procesSf  and  styloid  'processes.      It  is  a  single  bone  lying 


OSTEOLOGY.  25 

along  the  middle  line  of  tlie  body,  and  its  basilar  process 
forms  the  posterior  part  of  the  base  of  the  cranium.  It  is 
elongated  from  behind,  where  it  blends  with  the  condyles, 
forwards,  where  it  is  roughened,  coming  in  apposition 
with  OS  sphenoides.  It  widens  posteriorly  in  extending 
upwards  towards  the  roots  of  the  styloid  processes,  exter- 
nally to  the  condyles,  and  in  these  parts  we  see  a  large 
foramen  on  each  side,  condyloid,  through  which  the  lingual 
nerve  passes.  We  shall  simply  in  future  note  the  position 
of  the  foramina  of  the  skull,  as  a  more  detailed  description 
may  be  found  elsewhere. 

The  under  surface  is  convex,  and  anteriorly  presents 
roughened  depressions  for  attachment  of  rectus  capitis 
anticus  minor.  Posteriorly  it  presents  a  small  smooth 
process,  extending  between  the  condyles,  expanding  poste- 
riorly to  blend  with  the  upper  surface  in  forming  the 
inferior  part  of  foramen  magnum.  The  upj^er  j^ci'^t  is  con- 
cave in  all  parts,  most  so  posteriorly,  where  laterally  it 
presents  the  upper  openings  of  the  condyloid  foramina  ; 
while  anteriorly  its  external  margins  are  sharpened,  each 
forming  the  inner  boundary  oi  foramen  lacerum  basis  cranii. 
The  condyles  are  two  in  number,  forming  the  lateral 
boundaries  of  foramen  magnum.  They  are  articulatory 
prominences,  convex  in  all  parts,  superiorly  looking 
upwards  and  slightly  outwards,  inferiorly  downwards  and 
outwards.  Their  inner  aspect  is  upwards  and  inwards  ; 
superiorly  they  join  the  body  of  the  bone.  From  their 
external  angles  run  the  styloid  processes ;  inferiorly  they 
are  continued  on  to  the  basilar  processes,  converging,  but 
separated  by  a  smooth  concave  surface.  They  are  mainly 
separated  from  the  styloid  processes  by  deep  fossse,  which 
present  the  condyloid  foramina.  The  styloid  processes 
are  long,  and  extend  in  a  downward  direction,  being 
slightly  curled  inwards,  and  flattened  from  without  in- 
wards. They  afford  attachment  to  stylo-hyoideus,  stylo- 
maxillaris,  digastricus,  and  obliqui  capitis  superior  and 
anticus,  and  one  of  the  attoido-occipital  ligaments.  Their 
anterior  sarface  at  the  superior  part  is  roughened  for 
articulation  with  os  temporale  petrosum,  and  superiorly 
their  margin  is  continued  upwards  as  the  mastoid  ridge  to 
the  true  crest  of  the  bone.  The  body  of  the  occiput  is 
continued  upwards  from  the  superior  part  of  the  condyles 
and  styloid  processes  laterally,  centrally  from  the  superior 


26  OUTLINES    OF    EQUINE    ANATOMY. 

margin  of  foramen  magnum,  which  it  forms  by  means  of  a 
concave,  somewhat  sharp  margin.  It  presents  three  sur- 
faces :  the  anterior  internal  surface  is  firm,  and  presents  a 
number  of  depressions  for  accommodation  of  the  cerebellar 
convolutions,  from  which  it  is  separated  by  the  membranes 
of  the  brain.  The  posterior  Surface  is  bound  on  either  side 
by  the  mastoid  ridges,  and  meets  the  superior  in  forming  a 
prominent  ridge  with  a  backward  inclination,  crest  or  crista. 
This  surface  is  divided  into  two  parts  by  a  roughened  line 
extending  from  the  centre  of  the  crest  towards  foramen 
magnum.  To  this  the  cordiform  portion  of  ligamentum 
nuchse  is  attached ;  the  concave  roughened  surfaces  on 
either  side  of  it,  scabrous  pits,  afford  attachment  to  com- 
plex! major  and  minor  and  recti  capitis  major  and  minor 
postici.  To  the  crest  and  mastoid  ridges  are  attached 
temporalis,  obliquus  capitis  superior,  levator  humeri, 
trachelo  mastoideus,  splenius,  and  (to  the  crest)  some  of 
the  auricular  muscles.  The  superior  surface  of  the  bone 
forms  the  posterior  part  of  the  forehead,  and  is  roughened, 
for  from  it  commence  the  parietal  ridges.  Thus  it  affords 
attachment  slightly  to  temporalis  on  either  side,  and  ante- 
riorly presents  an  irregular  margin  dentated  centrally 
for  union  with  os  triquatrum,  squamous  laterally  for  union 
with  the  parietal  and  more  externally  with  the  squamous 
temporal  bone. 

OS  TRiaUATRUM  is  a  small  shield-shaped  portion  of 
bone,  with  a  smooth  and  flat  superior  surface  and  dentated 
margins  ;  ant ero -laterally  convex,  meeting  at  a  rounded 
point  anteriorly  for  union  with  the  parietals.  Posteriorly 
concave,  thus  presenting  two  prominent  posterior  angles, 
articulating  here  with  os  occipitis.  Its  iiuier  surface 
presents  the  ossific  tentorium,  a  remarkable  bony  promi- 
nence, with  three  concave  surfaces,  uniting  to  form  three 
sharp  margins,  one  at  each  side,  giving  attachment  to  the 
membranous  tentorium,  one  anteriorly  for  attachment  of 
the  posterior  margin  of  falx  cerebri. 

The  PARIETAL  BONES  are  flat  and  thin,  presenting 
two  surfaces  and  five  margins.  The  external  surface  is 
convex,  looking  upwards  and  outwards.  At  its  posterior 
part  it  presents  a  few  foramina  for  the  passage  of  men- 
ingeal arteries  to  the  coverings  of  the  brain.  It  is  divided 
into  two  parts  by  the  parietal  ridge,  a  slightly  prominent 
line  of  bone  passing  obliquely  outwards  from  the  anterior 


OSTEOLOGY. 


27 


part  of  tlie  crest  of  tlie  occiput  towards  tlie  orbital  process 
of  the  frontal  bone,  and  whicb  gives  attachment  to  auri- 
cular muscles.  The  outer  division  helps  to  form  the 
temporal  fossa,  and  affords  attachment  to  temporalis  ;  it  is 
continued  by  a  thin,  very  rough  squamous  surface,  on 
which  the  squamous  temporal  bone  rests.  The  inner 
portion  of  the  external  surface  is  immediately  subcu- 
taneous. The  poster 0 -internal  margin  articulates  by  suture 
with  OS  triquatrum,  the  inner  margin  similarly  with  its 
fellow.  The  anterior  margin  inwardly  presents  a  rough 
surface  for  squamous  articulation  with  os  frontis,  out- 
wardly the  outer  layer  of  the  bone  projects,  so  that  \t  rests 
on  OS  frontis.  The  external  margin  forms  the  thin  jagged 
edge  of  the  squamous  suture  with  the  squamous  temporal 
bone,  as  also  does  the  postero-external  margin,  which  meets 
with  the  postero -internal,  forming  a  point  which  articulates 
with  OS  occipitis.  The  inner  surface  of  the  bone  is  mostly 
covered  with  digital  impressions  for  accommodation  of  the 
cerebral  convolutions,  but  along  the  postero-external 
margin  has  a  smooth  groove  through  which  a  large  vein 
runs  to  torcular  herophili,  from  a  small  foramen  just 
above  the  mastoid  process  of  squamous  temporal  bone. 
Below  this  groove,  at  its  outer  part,  is  a  rough  surface  for 
union  with  the  petrous  temporal  bone. 

OS  FRONTIS  (one  of  which  is  found  on  each  side  of 
the  cranium)  forms  part  of  the  anterior  and  of  the 
superior  portion  of  the  cranium.  It  also  forms^  the 
supero-posterior  part  of  the  nasal  chamber  and  a  consider- 
able portion  of  the  inner  wall  of  the  orbit.  So  it  presents 
a  cranial,  a  facial,  and  an  orbital  plate.  The  facial  plate 
is  quadrilateral,  smooth  externally,  internally^  at  its  pos- 
terior part,  blends  with  the  cranial  plate,  at  its  anterior 
is  roughened,  helping  to  form  the  frontal  sinus.  The  outer 
surface  is  flat,  in  parts  convex,  and  subcutaneous  with 
exception  of  its  outer  margin  which  is  covered  by  orbicu- 
laris palpebrarum.  From  the  posterior  part  of  this 
margin  projects  the  orbital  process,  a  long  prominence, 
flattened  from  above  downwards,  externally  convex  in 
contact  with  the  orbicularis  palpebrarum,  intei-nally  con- 
cave in  contact  with  the  lachrymal  gland,  having  periorbi- 
tale  attached  to  its  posterior  margin.  Its  outer  extremity 
articulates  with  the  zygomatic  process  of  the  squamous 
temporal   bone;  its   anterior  margin  forms  the    superior 


28  OUTLINES    OF   EQUINE   ANATOMY. 

part  of  the  rim  of  the  orbit,  its  root  becomes  expanded  in 
becoming  attached  to  the  outer  edge  of  the  facial  plate, 
and  presents  the  supra-orbital  foramen.  The  anterior  part 
of  this  edge  forms  the  inner  part  of  the  rim  of  the  orbit, 
and  is  continuous  downwards  with  the  orbital  plate.  The 
anterior  margin  presents  a  laminated  squamous  surface  to 
the  outer  part  of  which  the  lachrymal,  to  the  inner  the 
nasal  bone  becomes  attached.  The  inner  margin  presents 
a  roughened  edge  for  apposition  with  its  fellow,  from  the 
anterior  part  of  which  a  thin  plate  of  bone  is  reflected 
downwards  to  form  the  inner  boundary  of  the  frontal  sinus 
lying  in  contact  with  its  fellow.  The  posterior  boundary  is 
squamous,  most  so  on  the  outer  side,  for  articulation  with 
the  parietal  bone.  The  cranial  plate  blends  superiorly 
with  the  posterior  part  of  the  under  surface  of  the  facial 
plate,  and  presents  digital  depression  for  the  cerebral 
convolutions.  Its  inner  margin  is  serrated  and  lies  in 
contact  with  its  fellow.  Its  inferior  margin  joins  the 
upper  part  of  the  crista  galli  and  cribriform  plates  of  the 
ethmoid.  Its  outer  margin  joins  the  orbital  plate.  The 
anterior  surface  helps  to  form  the  frontal  sinus,  and  from 
the  inner  margin  of  the  surface  runs  the  vertical  bony 
septum  which  inf eriorly  is  reflected  to  form  a  narrow  ledge 
of  bone  running  obliquely  forwards  and  upwards  in 
blending  anteriorly  with  the  facial  plate  in  a  sharp  point. 
The  orbital  plate  externally  is  concave,  forming  the  inner 
part  of  the  orbit.  Near  the  root  of  the  orbital  process  it 
presents  the  iibro-cartilaginous  loop  through  which  the 
superior  oblique  muscle  of  the  eye  plays.  Posteriorly  it  is 
continued  below  the  orbital  j^rocess,  helping  to  form  the 
temporal  fossa,  and  articulating  with  the  squamous  tem- 
poral bone.  This  plate  presents  a  deep  indentation,  in- 
feriorly  extending  upwards  towards  the  orbital  loop.  It 
terminates  in  a  point,  and  accommodates  the  orbital  surface 
of  OS  ethmoides,  which,  by  the  older  anatomists,  was 
termed  os  planum.  The  anterior  margin  inferiorly  gives 
attachment  to  os  palati ;  centrally  to  the  superior  maxil- 
lary bone ;  superiorly  to  the  lachrymal  bone.  The  inner 
surface  of  this  plate  posteriorly  is  separated  by  a  remark- 
able groove  from  the  cranial  surface,  and  has  a  squamous 
suture  with  the  ala  of  the  ethmoid  ;  centrally  it  gives  attach- 
ment to  the  cranial  plate  ;  anteriorly  forms  the  convex  outer 
wall  of  the  frontal  sinus.     At  the  extreme  postero-inferior 


OSTEOLOGY.  29 

part  this   plate  in  articulating  witli  os  etlimoides  forms 
foramen  orbitale  internum. 

OS  ETHMOIDES  forms  a  considerable  part  of  the  an- 
terior boundary  of  the  cranium,  and  consists  mainly  of  a 
body,  from  which  an  ala  projects  on  either  side,  and  a  re- 
markable process  projects  upwards  anteriorly.  The  body 
articulates  posteriorly  with  the  body  of  os  sphenoides  : 
here  it  is  rounded  and  solid,  but  anteriorly  it  presents  two 
large  cavities,  ethmoidal  sinuses,  indirectly  continuous  with 
the  nasal  chamber.  The  under  surface  presents  centrally 
a  small  convex  smooth  surface,  on  either  side  of  which  is 
roughened  for  squamous  suture  with  the  vomer.  Each  of 
the  sides  of  the  body  anteriorly  is  occupied  with  a  squamous 
surface  for  os  palati,  posteriorly  by  a  continuation  of  that 
on  the  posterior  part  for  os  sphenoides.  The  upper  surface 
looks  in  an  upward  and  slightly  backward  direction,  and 
is  concave.  Posteriorly  it  i:)resents  a  peculiar  depression 
separated  from  the  rest  of  this  surface  by  a  sharp  ridge, 
optic  fossa,  from  which  the  two  foramina  optici  pass  through 
the  substance  of  the  bone,  for  passage  of  the  optic  nerves, 
running  from  the  optic  decussation,  which  rests  in  the  fossa. 
The  wings  look  inward  and  slightly  upwards.  Their  upper 
surfaces  are  completely  occupied  in  formation  of  the  cere- 
bral cavity  ;  they  therefore  present  digital  impressions.  At 
the  line  of  junction  of  the  u?ider  surface  with  the  body  of  the 
bone  posteriorly  is  the  opening  (inferior)  of  the  optic  fora- 
men, and  in  front  of  this  is  a  smooth  groove,  which  by  union 
with  a  similar  depression  in  os  sphenoides  forms  foramen 
lacerum  orbitale.  The  outer  margin  of  this  surface  of  the  ala 
is  mainly  occupied  by  a  squamous  suture  for  union  with  the 
special  groove  in  os  frontis  ;  and  the  smooth  space  be- 
tween, by  some  anatomists  described  as  a  distinct  bone,  os 
planum,  serves  to  form  a  considerable  part  of  the  inner 
wall  of  the  orbit,  fitting  into  the  deep  depression  extending 
from  the  inferior  margin  of  the  orbital  plate  of  os  frontis. 
From  the  antero-superior  part  of  the  body  crista  galli  pro- 
cess runs  in  an  upward  direction,  to  join  superiorly  the 
infero- central  part  of  the  cranial  plates  of  ossa  frontis. 
Its  superior  extremity  is  enlarged,  and  presents  a  concave 
triangular  surface  for  os  frontis.  Its  posterior  margin  is 
sharp,  smooth  on  either  side  and  affords  attachment 
to  the  anterior  extremity  of  falx  cerebri.  Anteriorly 
it   presents  a  more    or    less    prominent    ridge,   extend- 


30  OUTLINES    OF    EQUINE    ANATOMY. 

ing  from  above  downwards,  continuous  anteriorly  as 
septum  nasi.  On  either  side  it  is  jagged,  and  continues 
as  far  as  the  anterior  margin  of  the  Avings  by  the  cribri- 
form pjates,  perforated  thin  layers  of  bone  through 
which  the  fibres  of  the  olfactory  nerves  pass,  and  which 
posteriorly  form  the  boundaries  of  depressions  olfactory 
fossa,  in  which  the  olfactory  bulbs  rest ;  anteriorly  have 
attached  to  them  certain  thin  plates  of  bone  curled  upon 
one  another  in  a  complex  manner,  forming  the  ethmoid 
cells,  a  direct  continuation  of  the  ethmoidal  sinuses  in  the 
body.  These  are  portions  of  bone  which  derive  their  nutri- 
ment directly  from  the  mucous  membrane  which  covers 
them,  having  no  special  periosteum.  In  that  mucous 
membrane  (and  also  that  of  the  superior  turbinated  bone) 
the  fibres  of  the  olfactory  nerve  are  distributed,  rendering 
it  the  organ  of  the  special  sense  of  smell. 

OS  SPHENOIDES  forms  the  major  portion  of  the  floor 
of  the  cranium,  and  is  situated  between  the  occiput  and 
OS  ethmoides.  It  consists  of  a  body  and  two  wings  with  two 
crura  or  legs.  The  upper  surface  of  the  body  is  irregularly 
concave,  receiving  the  name  sella  turcica.  Centrally  it 
supports  the  pituitary  body,  and  on  either  side  of  this  is  a 
depression  in  which  rests  the  cavernous  sinus,  while  extend- 
ing on  to  the  upper  surface  of  each  wing  on  each  side  we 
see  a  groove  for  the  superior  maxillary  division  of  the  fifth 
cranial  nerve,  running  forwards  to  join  the  suhsphenoid 
foramen  i7i  forming  foramen  rotundum.  This  is  separated 
anteriorly  by  a  thin  j)late  of  bone  from  a  smooth  groove, 
which  unites  with  another  on  os  ethmoides  to  ioYv^  foramen 
lacerum  orhitale.  The  posterior  extremity  presents  a  rough- 
ened ovoid  surface  for  articulation  with  the  anterior  ex- 
tremity of  the  basilar  process  of  the  occiput.  Anteriorly  is 
a  similar  surface  for  apposition  with  the  posterior  part  of 
the  body  of  the  ethmoid,  which  is  separated  on  each  side 
from  foramen  rotundum  by  a  thin  plate  of  bone,  which 
presents  a  small  squamous  surface  for  the  antero -internal 
part  of  the  wing  of  the  ethmoid.  The  under  surface  of 
the  body  is  convex,  tending  to  become  smooth  anteriorly. 
Posteriorly  it  is  rough  for  insertion  of  a  rectus  capitis 
anticus  major  on  either  side.  The  wing  of  os  sphenoides 
superiorly  is  concave  and  presents  an  irregular  surface, 
helping  to  form  the  cerebral  cavity.  Its  posterior  margin 
is  internally  sharp,  externally  rounded,  forming  the  anterior 


OSTEOLOGY.  '  31 

boundary  of  foramen  lacerum  basis  cranii.  Its  superior 
margin  presents  externally  a  squaiaous  serrated  surface  for 
the  squamous  temporal  bone.  In  the  angle  which  it  forms 
with  the  anterior  margin  is  foramen  pathetici.  The  anterior 
margin,  on  its  inner  edge,  articulates  with  the  wing  of  os 
ethmoides,  superiorly  presenting  the  smooth  groove  which 
forms  foramen  lacerum  orbitale,  more  externally  foramen 
rotundum,  and  on  its  outer  edge  a  ridge  to  which  peri- 
orbitale  is  attached,  which  terminates  inferiorly  in  an  elon- 
gated process,  flattened  from  side  to  side.  This  is  the 
crus  of  the  bone.  Its  siqjerior  margin  and  anterior  extre- 
mity articulate  with  os  palati ;  its  inner  surface  posteriorly 
with  OS  pterygoideum,  and  to  its  inferior  margin  are 
attached  masseter  internus  and  pterygoideus. 

OS  TEMPORALE   SaUAMOSUM  (one  on  each  side  of 
the  head)  is    situated   at   the  postero-lateral  part  of  the 
head,  and  is  so  named  because  its  main  portion  is  almost 
wholly  occupied  in  squamosal  connection  with  the  neigh- 
bouring   bones.     It  is  divided  into  two  parts — body  and 
zygoma.     The  inner  surface  of  the  body  superiorly  along 
its  whole  length  articulates  with  the   parietal  bone.     Its 
anterior  margin  joins  os  frontis  ;  antero- inferiorly  it  joins 
the  wing  of  os  sphenoides  ;  postero -inferiorly  it  presents  a 
deep  notch,  into  which  the  petrous  temporal  bone  with  the 
external  auditory  process  fits.     The  posterior  margin  unites 
with  the  petrous  temporal  bone,  and  at  its  extreme  posterior 
part  with  os  occipitis.     The  central  part  of  the  inner  surface 
is  smooth,  and  assists  to  form  the  wall  of  the  cranium.     The 
external  surface  is  divided  into  two  almost  equal  parts  by 
a  line  running  from  the  postero-superior  to  the  antero- 
inferior angle,  from  the  anterior  part  of  which  the  zygoma 
commences.     The  space  above  this  line  helps  to  form  the 
temporal  fossa,  having   temporalis  attached  to    it,   while 
superiorly  it  presents  some  foramina.    The  inferior  division 
of  this  surface  is  smooth  and  centrally  presents  a  groove, 
the  inferior  opening  of  the  canal  between  this  and  the 
parietal  bone.     Just  in  front  of  this  is  a  small  rounded 
prominence,  the  mastoid  process,  to  which  is  attached  one 
of  the  ligaments  of    the    temporo -maxillary  articulation. 
The  zygoma  is  a  large  process,  which  is  very  thin,  flattened 
from  above  downwards,  running  directly  outwards  at  its 
origin.     It  is  then  twisted  from  below  upwards  (so  that  its 
outer  margin  becomes  superiorly  placed),  and  runs  in  a 


32  OUTLINES    OF    EQUINE    ANATOMY. 

forward  direction.  Its  superior  margin  anteriorly  presents 
a  roughened  prominence,  to  whicli  the  outer  extremity  of 
the  orbital  process  of  os  frontis  is  united.  In  front  of 
this,  the  inner  surface,  is  concave,  forming  part  of  the  orbit ; 
the  outer  surface  presents  a  squamous  suture,  terminating 
anteriorly  in  a  point  for  the  zygomatic  or  malar  bone. 
The  rest  of  the  outer  surface  affords  attachment  to  masseter 
externus.  The  superior  surface,  at  its  junction  with  the 
body,  forms  a  deep,  smooth,  rounded  groove,  in  which  the 
coracoid  process  of  the  inferior  maxilla  fits.  The  under 
surface  presents  the  glenoid  cavity  coate  i  with  articular 
cartilage,  extending  from  without  inwards  on  to  the  body, 
rounded  posteriorly  by  the  mastoid  process  ;  it  articulates 
with  the  condyle  of  the  inferior  maxilla  through  the  medium 
of  a  disc  of  cartilage. 

OS  TEMPORAL  PETROSTJM  (Pair)  is  an  extremely 
irregular  bone,  wedged  in  between  the  occipital,  parietal, 
and  squamous  temporal  bones.  Its  posterior  surface  lies  in 
contact  with  os  occipitis,  its  anterior  superior  with  the 
parietal,  inferiorly  with  the  squamous  temporal  bone.  It 
is  the  hardest  bone  in  the  body,  and  co7itains  the  organ  of 
hearing  (as  will  be  afterwards  described).  Its  inner  sur- 
face helps  to  form  the  inner  surface  of  the  cranium,  and 
presents  digital  impressions,  with  centrally /oramew  audi- 
torium  internum.  The  external  surface  is  very  rough  and 
irregular ;  superiorly  it  assists  in  forming  the  mastoid 
ridge,  giving  attachments  to  several  of  the  cervical  muscles  ; 
centrally  it  presents  the  external  auditory  process,  to 
which  the  annular  cartilage  of  the  ear  is  attached,  and 
which  is  perforated  by  the  external  auditory  hiatus,  which 
extends  inwards  as  far  as  the  tympanum.  Below  and  in 
front  of  this  there  is  a  prominence,  which  looks  as  if  a 
round  peg  had  been  driven  into  the  bone ;  this  is  the 
hyoid  process,  to  which  the  antero-superior  angle  of  the 
long  cornu  of  os  hyoides  is  united  by  fibro- cartilage. 
Immediately  below  this  is  a  rounded,  roughened  protu- 
berance, denoting  the  situation  of  the  mastoid  cells  inside 
the  bone  ;  hence  it  is  termed  the  mastoid  process.  In  front 
of  it  is  an  elongated,  sharp  process,  the  styloid  process,  to 
which  tensor  palati  and  stylo-pharyngeus  are  attached,  and 
just  below  and  behind  it  is  the  styloid  foramen,  from  which 
the  Eustachian  tube  passes  to  the  pharynx. 


OSTEOLOGY.  33 


BONES  OF  THE  FACE 


are  nine  pairs  and  two  single  bones.     We  sliall  first  examine 
the  pairs. 

OS  NASI  is  a  fiat  bone,  forming  tbe  major  part  of  the 
roof  of  the  nasal  chamber;  presents  two  surfaces,  two 
margins,  a  base,  and  an  apex.  The  lase  of  this  bone  has  a 
squamous  laminated  surface  for  union  with  os  frontis. 
The  inner  margin  is  straight,  and  lies  in  apposition  with  the 
corresponding  part  of  its  fellow.  The  outer  margin  meets 
it  at  an  extremely  acute  angle,  and  as  the  anterior  part  of 
the  outer  margin  is  free,  the  two  points  coming  together 
produce  a  remarkable  prominence,  to  which  the  nasal  car- 
tilages are  attached,  and  which  is  termed  the  nasal  peak. 
From  the  external  surface  of  the  bone,  near  the  outer  margin 
of  the  nasal  peak,  dilator  naris  superior  arises  ;  behind  this 
the  margin  is  in  apposition  with  the  upper  extremity  of 
the  superior  process  of  the  anterior  maxillary  bone.  It 
then  presents  thin  horizontal  plates  fitting  into  os  niaxil- 
lare  superius,  and  at  the  outer  angle  of  the  base  is  a  line  of 
union  with  os  lachrymale.  The  superior  surface  is  convex  ; 
inclined  obliquely  outwards  over  it  passes  nasalis  longus 
labii  superioris.  The  inner  surface,  correspondingly  con- 
cave, is  partly  occupied  by  the  expanded  upper  portion  of 
septum  nasi,  but  inclined  to  its  outer  side  it  presents  a 
ridge  to  which  is  attached  OS  turbinatum  superius.  The 
turbinated  bones  are  extremely  thin  and  friable  in  the 
dried  subject,  but  when  fresh  they  are  coated  on  both  sides 
by  mucous  membrane,  which  renders  them  elastic.  Each 
of  them  consists  of  two  portions,  one  anteriorly  placed, 
belonging  to  the  nasal  chamber,  the  other  to  the  sinuses  of 
the  head.  These  bones  are  supplied  with  nutriment  by 
their  investing  mucous  membrane  ;  they  therefore  have  no 
periosteum.  They  will  be  noticed  more  particularly  in  our 
description  of  the  nasal  chambers  and  the  sinuses  of  the 
head. 

Os  turbinatum  inferius  is  attached  to  the  nasal  surface 
of  the  facial  plate  of  the  superior  maxillary  bone. 

Os  maxillare  anterius  is  situated  at  the  anterior  part  of 
the  upper  jaw,  lodges  the  superior  incisors,  and  forms  the 
outer  and  inferior  boundary  of  the  anterior  opening  into 
the  nasal  fossae  of  the  skeleton ;  it  consists  of  a  body  and 

3 


34  OUTLINES    OF   EQUINE   ANATOMY. 

two  processes.  The  body  is  externally  convex,  affording 
attachment  to  levator  labii  superioris.  Its  internal  surface 
lies  in  contact  with  its  fellow  by  a  broad  roughened  surface, 
and  the  two  bones  here  together  form  foramen  incisiorum, 
running  from  the  roof  of  the  mouth  at  its  extreme  ante- 
rior part.  The  anterior  attachment  of  septum  nasi  extends 
on  the  bone  as  far  as  this  foramen.  The  inferior  margin 
of  the  body  presents  on  each  side  three  alveolar  cavities, 
into  which  the  incisors  lit.  These  are  conical  depressions, 
separated  from  each  other  by  thin  bony  plates ;  thus  the 
two  central  incisors  have  between  them  two  bony  laminae. 
Behind  the  convex  alveolar  line  is  a  smooth  portion  of 
the  lower  margin  of  the  bone,  and  behind  this  is  a  ^portion 
of  the  alveolar  cavity  for  the  tush,  which  is  completed  by  the 
superior  maxillary  bone.  From  the  supero-posterior  part 
of  the  body  an  elongated  process  passes  obliquely  upwards 
and  backwards.  It^  superior  margin  Y\m^  irom  the  upper 
portion  of  the  symjjhysis,  first  outwards,  then  upwards,  as 
far  as  os  naris.  It  is  rounded,  to  its  external  surface 
dilator  naris  inferior  is  attached,  and  it  winds  round 
towards  the  false  nostril.  Its  posterior  margin,  inferiorly 
by  squamous  suture,  superiorly  by  schindylesis,  is  in  con- 
nection with  the  superior  maxillary  bone.  The  up^er 
margin  is  united  to  the  anterior  part  of  the  roughed  por- 
tion of  the  outer  margin  of  the  os  nasi.  The  inner  surface 
forms  the  anterior  margin  of  the  lateral  boundary  of  the 
nasal  chamber.  The  inferior  surface  of  the  body  of  this 
bone  slopes  obliquely  upwards  and  backwards,  and  centrally 
terminates  in  a  thin  process,  the  p>alatine,  running  back- 
wards towards  the  palatine  process  of  the  superior  maxillary 
bone.  It  is  flattened  from  above  downwards  ;  its  extreme 
postero-superior  parts  in  some  cases  is  in  apposition  with 
the  anterior  extremity  of  the  vomer ;  it  forms  the  inner 
boundary  of  a  space,  incisive  opening,  which  is  generally 
filled  with  cartilaginous  matter  continuous  superiorly  with 
septum  nasi,  embedded  in  which  is  the  organ  of  Jacobson. 
Os  maxillare  superius  is  a  large  bone,  with  its  fellow 
forming  a  very  considerable  portion  of  the  face.  It  assists 
in  forming  several  cavities,  and  completely  forms  one  of 
the  facial  sinuses,  the  inferior  maxillary.  These  sinuses, 
however,  are  only  found  markedly  developed  in  the  adult. 
It  presents  two  surfaces  and  four  margins.  The  superior 
margin  is  irregular,  being  in  apposition  with  the  outer 


OSTEOLOGY.  35 

margin  of  the  os  nasi ;  it  is  but  half  the  length  of  the 
inferior.  The  anterior  margin  slopes  obliquely  downwards 
and  forwards,  and  joins  the  posterior  margin  of  the  nasal 
process  of  the  anterior  maxilla.  It  meets  the  inferior  margin 
at  an  acute  angle  in  forming  the  posterior  boundary  of  the 
alveolar  cavity  for  the  tush.  The  posterior  margin  presents 
an  irregular  concavity  looking  upwards.  It  is  a  rough 
squamosal  surface  extending  into  the  outer  part  of  the  bone, 
increasing  in  width  from  above  downwards,  superiorly  in  ap- 
position with  the  lachrymal,  inferiorly  with  the  malar  bone. 
This  surface  terminates  above  in  a  projecting  point,  which 
slightly  meets  the  squamous  temporal  bone.  The  inferior 
surface  of  the  projection  is  smooth  for  the  passage  of  the 
superior  varicose  vein  of  the  face ;  below,  and  slightly 
behind,  is  an  irregular  prominence,  tuberosity,  to  which 
buccinator  and  retractor  labii  inferiosis  are  attached.  The 
inferior  margin  along  the  greater  part  of  its  length  is  occu- 
pied by  the  alveolar  cavities  for  the  upper  molars.  These 
consist  of  a  series  of  deep  square  cavities,  separating  the 
bone  into  two  plates,  and  separated  from  one  another  by 
thin  bony  septa.  Their  walls  correspond  to  the  external 
surface  of  the  teeth,  into  the  grooves  of  which  the  bony 
matter  is  moulded.  They  are  six  in  number  ;  the  first  and 
last  cavities  of  the  series  are  triangular,  and  sometimes  at 
the  anterior  angle  of  the  first  is  a  small  alveolar  cavity  in 
which  the  premolar  or  "  wolf's  tooth  "  is  situated.  In 
front  of  this  the  inferior  margin  is  smooth  and  rounded  to 
its  anterior  extremity.  The  external  surface  slopes  obliquely 
downwards  and  outwards.  From  about  the  centre  of  the 
articulatory  surface  of  the  posterior  margin  (which  en- 
croaches considerably  upon  the  surface)  the  anterior  ex- 
tremity of  the  zygomatic  ridge  runs  forward  for  a  short 
distance.  It  terminates  about  opposite  the  second  molar 
tooth  ;  to  its  under  surface  are  attached  masseter  externus 
and  zygomaticus,  just  in  front  of  its  anterior  extremity 
retractor  labii  superioris  arises.  Buccinator  posteriorly  and 
caninus  anteriorly  arise  from  this  surface  just  above  the 
inferior  margin  ;  and  between  the  former  muscle  and  the 
zygomatic  spine  is  the  superior  varicose  vein  of  the  face. 
The  superior  maxillary  or  infra-orhitar  foramen  is  situated 
above  and  in  front  of  the  zygomatic  spine  ;  through  it  the 
major  portion  of  the  dental  branch  of  the  superior  maxillary 
division   of    the  fifth  nerve  (after   passing  through    the 


36  OUTLINES    OF    EQUINE    ANATOMY. 

canalis  infra  orbitale,  a  special  chanuel  of  the  "bone  which 
runs  through  the  maxillary  sinus)  emerges  with  an  accom-  • 
panying  artery,  both  run  forwards  concealed  from  view  by 
levator  labii  superioris  alseque  nasi.  From  the  point  of 
junction  of  the  malar,  lachrymal,  and  superior  maxillary 
bones,  nasalis  longus  labii  superioris  arises.  A  considerable 
portion  of  the  inner  surface  of  this  bone  is  occupied  in 
forming  the  outer  wall  of  the  nasal  chamber.  Along  the 
central  line  extending  from  before  backwards  is  a  ridge  to 
which  the  inferior  turbinated  bone  is  attached.  At  about 
the  centre  of  the  bone  this  terminates  in  bifurcating,  form- 
ing two  lines,  one  of  which  runs  upwards  and  backwards, 
the  other  downwards  and  backwards,  mapping  out  that 
portion  of  bone  which  forms  the  inferior  maxillary  sinus. 
The  extreme  inferior  margin  affords  attachment  to  the 
gums  of  the  roof  of  the  mouth ;  higher  up  is  a  groove 
running  forwards  for  the  palatine  artery,  and  above  this  a 
horizontal  process,  palatine  process,  projects  inwards.  It 
extends  neither  as  far  as  the  anterior  nor  as  the  posterior 
extremity  of  the  bone,  but  anteriorly,  gradually  diminishes 
in  size  to  terminate  imperceptibly ;  posteriorly  presents  a 
squamous  surface  extending  on  to  the  small  part  of  the 
tuberosity  for  union  with  the  palate  bone.  This  surface 
presents  a  smooth  groove,  which  helps  to  form  the  palatine 
canal.  The  free  margin  presents  numerous  spiculse  of  bone, 
which  serve  to  keep  it  closely  in  apposition  with  the  palatine 
process  of  its  fellow,  and  the  two  together  form  a  groove 
into  which  the  anterior  part  of  the  inferior  margin  of  the 
vomer  fits.  The  iij)per  surface  of  this  process  helps  to  form 
the  floor  of  the  nasal  chamber,  the  inferior  surface  is 
covered  by  the  mucous  membrane  of  the  hard  palate,  with 
its  rich  venous  plexus.  This  bone  assists  in  forming  the 
superior  maxillary  sinus  through  which  two  bony  canals 
pass,  the  canalis  infra  orbitale,  and  the  bony  covering  of  the 
ductus  ad  nasum. 

OS  LACHRYMALE  forms  the  antero -internal  part  of 
the  orbit,  assisting  in  forming  its  margin,  thus  being  bent 
upon  itself  in  such  a  manner  as  to  present  two  plates, 
separated  by  the  concave  marginal  border,  which  is  for  tbe 
most  part  smooth,  but  centrally  rather  rough.  The  exter- 
nal surface,  therefore,  as  a  whole,  is  convex,  but  it  consists 
of  two  concave  plates.  The  anterior  is  the  facial  plate.  It 
presents  at  about  its  centre  a  tubercle  (lachrymal)  to  which 


OSTEOLOGY.  O  / 

the  orbicularis  palpebrarum  is  attached.  Above  this  it 
gives  partial  attachment  to  labii  superioris  alseque  nasi, 
below  to  nasalis  longus  labii  superioris.  The  posterior  or 
orbital  plate  is  funnel-shaped,  converging  from  all  points 
to  towards  the  lachrymal  foramen^  situated  just  behind  the 
centre  of  the  marginal  border.  To  this  bone  near  this 
foramen  is  attached  the  inferior  oblique  muscle  of  the  eye- 
ball, and  in  it  rests  the  lachrymal  sac  from  which  the 
ductus  ad  nasum  is  continued  forwards  through  a  bony 
canal,  running  along  and  attached  to  the  internal  surface 
of  the  facial  plate  of  the  bone.  The  i7iner  surface  of  the 
bone  assists  in  forming  the  superior  maxillary  sinus,  and  is 
therefore  covered  with  mucous  membrane.  The  anterior 
margin  is  in  contact  with  os  nasi  and  also  with  the  supe- 
rior maxillary  bone,  which  extends  along  the  whole  length 
of  the  inferior  margin,  along  the  inner  edge,  while  the 
malar  bone  has  a  squamous  union  with  a  considerable  por- 
tion of  the  outer  edge.  The  extreme  posterior  part  of  this 
margin  is  smooth.  The  superior  margin  has  a  squamous 
union  with  os  f  rontis,  but  at  the  posterior  angle,  where  this 
margin  and  the  inferior  meet,  the  lachrymal  bone  comes  in 
contact  with  os  palati. 

OS  PALATI  forms  the  anterior,  posterior,  and  outer 
boundary  of  the  posterior  naris.  It  is  very  irregular,  but 
mainly  consists  of  a  bony  plate  elongated  from  behind 
forwards.  This  plate  is  convex  on  its  internal  surface,  and 
posteriorly  is  divided  into  two  equal  parts  by  a  prominent 
ridge.  The  upper  part  is  articulatory  supero-posteriorly 
for  union  with  the  lateral  part  of  the  body  of  ethmoides  ; 
in  front  of  this  os  f rontis  occupies  a  small  space ;  os 
lachrymale,  a  still  smaller  ni  front  of  that ;  but  the  greater 
part  of  this  division  is  covered  with  mucous  membrane, 
assisting  to  form  the  ethmoid  sinus.  Below  the  articula- 
tion with  OS  f rontis  is  foramen  spheno-palati7ium,  which  is 
continued  by  a  groove  on  to  the  inferior  part,  which,  with 
the  inferior  part  of  the  ridge,  posteriorly  is  united  to  the 
])terygoid  and  (more  inwardly)  the  vomer.  Anteriorly 
this  part  becomes  much  prolonged  and  is  smooth  and 
concave,  forming  the  posterior  boundary  of  the  posterior 
nares.  It  becomes  twisted  from  below  upwards  at  its 
anterior  extremity,  thus  forming  a  peculiar  process, 
palatine,  the  inner  margin  of  which  is  smooth,  rounded, 
concave,  and  coated  with  mucous  membrane  forming  the 


38  OUTLINES    OF    EQUINE    ANATOMY. 

anterior  and  external  boundary  of  tlie  posterior  naris  in 
the  skeleton.  Its  free  extremity  unites  with  its  fellow  ante- 
riorly at  a  symphysis,  and  thus  the  two  bones  form  a 
''■  jpalatine  arcli,'^  to  which,  in  the  fresh  subject,  the  fibrous 
layer  of  the  fixed  portion  of  the  soft  palate  is  attached. 
The  free  margin  of  the  ridge  on  the  inner  surface  of  the 
bone  is  united  to  the  vomer,  and  by  the  groove  of  that  bone 
separated  from  its  fellow.  The  external  margin  of  the 
palatine  process  is  convex,  and  presents  a  serrated  edge  for 
union  with  the  palatine  process  of  the  superior  maxilla. 
Posteriorly  this  roughened  surface  increases  in  size,  pre- 
senting a  very  wide  squamous  surface  for  union  with  the 
inner  surface  of  the  tuberosity  of  the  superior  maxilla. 
This  surface  is  rough  in  all  parts  except  at  a  central 
groove  running  forwards,  which  combines  with  a  similar 
depression  on  the  maxillary  surface  to  form  the  palatine 
canal.  Behind  this  the  bone  is  smooth  ;  it  is  over  here  the 
superior  maxillary  division  of  the  sixth  nerve  and  the 
internal  maxillary  artery  course  in  their  way  from  the 
sphenoidal  to  the  maxillary  hiatus.  The  extreme  posterior 
part  of  the  inferior  margin  articulates  with  the  crus  of  os 
sphenoides,  assisting  to  form  the  pterygoid  ridge,  to  the 
superior  part  of  the  internal  surface  of  which  is  attached 
the  pterygoid  bone. 

OS  PTERYGOIDEUM  is  a  small  plate  of  bone  attached 
to  the  under  surface  of  the  cranium  at  its  junction  with  the 
face ;  consists  of  two  parts,  the  anterior  of  which  is  flattened 
from  side  to  side,  the  posterior  from  above  downwards 
and  is  the  widest  and  thinnest.  The  anterior  iorms  a  small 
tuberous  prominence,  attached  to  the  inner  surface  of  the 
palatine  bone,  curved  slightly  outwards  at  its  extremity, 
thus  producing  a  groove  through  which  tensor  palati  plays 
(bound  down  by  the  pterygoid  ligament) .  The  superior  sur- 
face of  the  posterior  part  articulates  with  ossa  sphenoides 
and  palati,  and  its  inner  margin  meets  the  vomer.  To  its 
under  surface  masseter  internus  and  pterygoideus  gain 
either  direct  or  indirect  attachment. 

OS  ZYGOMATICUM  OR  THE  MALAR  BONE  forms  the 
major  portion  of  the  outer  boundary  of  the  orbit.  It  is 
pyramidal,  presenting  three  surfaces,  three  margins,  a  base 
and  an  apex.  The  external  surface  is  for  the  most  part 
convex,  anteriorly  it  is  flat,  affording  attachment  to 
nasalis   longus  labii    superioris.      Its  inferior  margin  is 


OSTEOLOGY.  39 

surmounted  by  the  middle  portion  of  the  zygomatic  ridge, 
to  which  masseter  externus  is  attached.  The  superior 
surface  is  concave,  occupies  the  centre  of  the  bone,  being 
continued  neither  to  the  superior  extremity  nor  to  the 
inferior,  and  assists  in  foruiing  the  orbit.  The  internal 
surface  is  concave,  and  wholly  occupied  by  a  squamous 
surface ;  the  major  portion  lies  in  apposition  with  the 
superior  maxillary  bone,  but  at  the  antero-superior  angle  it 
unites  with  the  lachrymal  bone.  The  base,  external  and 
internal  margins  are  the  sharpened  edges  of  the  squamous 
surface.  The  superior  margin  anteriorly  is  serrated  for 
union  with  os  lachrymale,  centrally  smooth,  rounded,  and 
concave,  forming  the  outer  margin  of  the  orbit ;  pos- 
teriorly it  is  continuous  at  the  apex  on  to  the  superior 
surface,  forming  a  squamous  facet  for  the  antero-external 
part  of  the  zygomatic  process  of  the  squamous  temporal 
bone. 

The  VOMER,  so  named  from  the  resemblance  of  the 
corresponding  bone  in  man  to  a  ploughshare,  is  the  only 
single  bone  in  the  facial  portion  of  the  upper  jaw. 
It  presents  two  margins,  two  extremities,  and  two  surfaces. 
This  bone  posteriorly  forms  the  line  of  division  of  the 
posterior  nares  ;  anteriorly  it  is  continued  almost  as  far  as 
the  anterior  naris  on  the  floor  of  the  nasal  cavity  between 
the  two  chambers.  Its  inferior  border  anteriorly  presents 
a  roughened  articulatory  surface,  which  fits  into  a  groove 
formed  by  the  junction  of  the  palatine  processes  of  the 
superior  and  anterior  maxillae  of  one  side  with  the  corre- 
sponding parts  of  the  other,  being  an  example  of  the  form 
of  joint  known  as  schindylesis.  The  posterior  part  of  th^ 
inferior  border  is  covered  by  mucous  membrane  ;  centrally 
it  is  sharp,  dividing  the  posterior  nares,  posteriorly  expands, 
terminating  on  either  side  in  a  sharp  point,  which  is  con- 
cealed by  the  pterygoid  bone.  The  superior  margin  con- 
sists of  two  thin  plates  of  bone  passing  upwards  one  on 
each  side  to  form  a  groove  into  which  septum  nasi  fits. 
These  plates  gradually  increase  in  length  (and  the  groove 
accordingly  in  depth)  from  before  backwards  to  about  the 
anterior  part  of  the  posterior  third  of  the  bone,  where  they 
become  widened,  presenting  on  their  external  surfaces 
concave  squamous  articulations  for  the  inner  ridges  of  the 
palatine  bones.  At  the  extreme  posterior  part  they  meet 
the  under  surface  of  the  ethmoid  and  sometimes  extend  as 


40  outlitntes  of  equine  anatomy. 

far  as  os  spHenoides.  The  groove  also  becomes  wider  here, 
receiving  the  postero -inferior  thickened  angle  of  septum 
nasi.  The  apex  of  the  hone  rests  on  the  palatine  processes 
of  the  anterior  maxillae.  The  hase  is  formed  by  the  pos- 
terior angular  prolongations  with  their  separating  depres- 
sion. It  consists  of  a  sharp  concave  ridge.  The  surfaces 
are  the  outer  surfaces  of  the  thin  plates,  and  are  covered 
by  the  Schneiderian  mucous  membrane. 

THE  LOWER  JAW 

is  formed  by  a  single  bone,  the  INFERIOR  MAXILLA, 
which  articulates  with  the  upper  jaw  only  at  the  glenoid 
cavities  of  the  squamous  temporal  bones,  though  connected 
with  it  by  soft  structures  in  many  parts  in  the  fresh  sub- 
ject. It  consists  of  two  exactly  similar  halves  united  to- 
gether by  the  symphysis  at  the  interior  part.  Between  these 
anteriorly  is  situated  the  tongue,  postero- superiorly  the 
l)harynx  and  guttural  pouches.  Each  side  of  the  bone 
presents  two  surfaces,  two  margins,  and  two  extremities. 
The  superior  extremity  is  divided  into  two  parts  by  a  deep 
notch  through  which  a  branch  of  nerve  passes. 

The  anterior  part  is  the  coracoid  process,  which  runs 
upwards  for  a  considerable  distance,  inclined  backwards. 
It  is  flattened  from  side  to  side  and  rests  in  the  temjDoral 
fossa.  Its  inner  surface  affords  attachment  to  temporalis . 
The  posterior  part  is  the  condyle  ;  it  is  elongated  from  side 
to  side,  convex  in  every  direction,  with  a  slight  oblique 
inclination  inwards.  It  is  coated  with  articular  cartilage, 
and  through  the  medium  of  the  inter-articular  disc  of  car- 
tilage, articulates  with  the  glenoid  cavity  of  the  squamous 
temporal  bone.  The  condyle  affords  attachment  to  the 
capsular  ligament  around  its  margin,  externally  also  to  its 
strengthening  accessory  band.  Below  the  condyle  on  the 
inner  side  pterygoideus  is  inserted,  and  here  the  external 
carotid  artery  terminates  its  temporal  branch,  winding  round 
the  posterior  margin  of  the  jaw.  The  anterior  extremity  or 
body  is  flattened  from  above  downwards,  presenting  two 
surfaces  and  two  margins.  The  superior  surface  is  concave, 
sloping  from  without  inwards,  covered  by  the  mucous 
membrane  of  the  mouth,  from  which  internally  frsenum 
linguse  passes.  The  inferior  surface  is  convex,  sloping 
from  the  external  to  the  internal  margin  and  backwards. 


OSTEOLOGY.  41 

Superiorly  it  is  covered  by  tlie  gums  ;  below  tliis  depressor 
labii  inferioris  lias  its  origin.  The  external  margin  presents 
three  alveolar  cavities  for  the  lower  incisors,  slightly 
smaller  than  those  in  the  upper  jaw,  and  behind  these, 
after  a  short  interval,  the  alveolar  cavitij  for  the  tush,  which 
is  more  anteriorly  placed  than  its  superior  corresponding 
cavity.  The  internal  "mar gin  is  rough,  and  by  uniting 
with  its  fellow  forms  the  symphysis.  Behind  the  body 
the  bone  is  constricted,  forming  the  neck,  which  partly  lies 
in  contact  with  the  buccal  mucous  membrane.  Its  external 
surface  superiorly  presents  the  curved  line  of  attachment 
of  carinus  ;  below  this  is  the  anterior  maxillary  foramen  or 
foramen  menti.  Below  this  the  bone  is  subcutaneous. 
Both  its  superior  and  its  inferior  margins  are  rounded. 
The  latter  to  its  inner  side  has  digastricus  attached  as  far 
forward  as  the  symphysis.  The  neck  terminates  posteriorly 
where  the  alveolar  cavities  of  the  molars  commence.  They 
resemble  iu  general  cliaracters  and  number  those  of  the 
upper  jaw,  and  occupy  a  considerable  portion  of  the  superior 
margin  of  the  bone,  which  extends  gradually  backwards 
and  upwards,  and  which  from  the  last  alveolar  cavity 
curves  upwards  to  join  the  anterior  margin  of  the  coracoid 
process,  aifording  attachment  to  buccinator  and  to  re- 
tractor labii  inferioris.  Buccinator  also  becomes  attached 
to  the  bone  up  against  the  alveolar  cavities  on  the  external 
surface  ;  below  this  retractor  labii  inferioris  runs  forwards, 
the  rest  of  the  anterior  part  of  this  surface  is  separated  from 
the  skin  only  by  retractor  anguli  oris.  But  behind  the 
molars  the  bone  becomes  much  expanded,  in  consequence 
of  increased  convexity  of  the  inferior  margin,  which  pro- 
trudes postero-inferiorly  forming  the  angle  of  the  jaw  to 
which  sterno-and  stylo-maxillaris  are  attached,  the  latter 
to  the  inner,  the  former  to  the  outer  edge.  The  margin 
above  this  is  thickened  and  tuberous.  The  parotid  gland 
is  in  contact  with  it.  The  expanded  portion  is  termed  the 
ramus  or  branch,  and  being  concave  both  externally  and 
internally  its  central  portion  is  very  thin.  On  both  sur- 
faces it  presents  roughened  ridges  extending  from  above 
downwards  which  on  the  external  surface  serve  to  give 
attachment  to  masseter  externus,  on  the  inner  side  to 
masseter  internus,  which  latter  muscle  hides  the  posterior 
maxillary  foramen  to  which  the  inferior  dental  artery  and 
nerve  pass,  and  having  entered  it  course  along  below  the 


42  OUTLINES    OF    EQUiyE    ANATOMY. 

fangs  of  tlie  molars  as  far  as  the  anterior  maxillary  fora- 
men, where  each  sends  a  branch  outwards,  while  the  main 
portion  continues  on  in  the  bone  to  supply  the  incisors 
and  tush.  The  upper  edge  of  the  internal  surface  up 
against  the  molar  teeth  is  termed  the  alveolar  ridge,  and 
affords  attachment  to  mylo-hyoideus,  the  external  surface 
of  which  muscle  lies  in  contact  with  the  bone  as  far  down 
as  the  inferior  margin,  where  the  submental  branch  of  the 
submaxillary  artery  passes  forwards,  just  abovethe  attach- 
ment of  digastricus.  Below  this  the  inferior  margin  of  the 
bone  is  rounded  and  covered  with  panniculus  ;  at  the  com- 
mencement of  the  ramus  it  presents  one  or  more  promi- 
nences, which  serve  to  mark  where  the  submaxillary  vessels 
and  the  parotid  duct  wind  round  the  jaw. 

THE  VERTEBRA. 

The  distinctive  characteristic  of  vertebrata  is  the  pos- 
session of  a  central  chain  of  bones  forming  a  spinal  column. 
The  chain  is  composed  of  vertebrae,  and  to  the  vertebrae 
all  the  other  bones  of  the  body  are  appended,  so  that  each 
vertebra  with  its  bony  appendages  constitutes  a  vertebral 
segment  of  the  body.  These  vertebral  segments  differ  in 
number  in  different  animals,  and  frequently  vary  in  animals 
of  the  same  species.  They  are  between  fifty  and  sixty  in 
number  in  the  horse.  A  complete  or  typical  vertebral 
segment  consists  of  two  similar  arches  united  in  forming 
a  rounded  body  or  centrum.  One  is  placed  superiorly  to 
the  centrum,  and  as  it  encloses  the  nerve-centres  of  animal 
life  is  termed  the  neural  arch;  the  other  is  inferiorly 
placed,  and  is  termed  the  hcemal  arch, — it  encloses  the 
organs  of  vegetative  life,  including  circulation,  respiration, 
digestion,  and  involuntary  motion.  Each  arch  may  be 
divided  into  five  parts ;  those  of  the  neural  arch  are  : 
pedicles,  running  upwards  from  the  supero-lateral  parts 
of  the  body  ;  lamince,  running  from  the  upper  extremities 
of  the  pedicles  to  meet  in  the  central  line,  and  from  the 
point  of  junction  the  neural  or  superior  spinous  process  runs 
upwards.  These  parts  may  be  found  in  almost  all  the 
vertebral  segments,  though  only  in  a  rudimentary  con- 
dition in  the  coccygeal  region.  The  haemal  arch  can  be 
recognised  only  in  the  dorsal,  though  found  under  ex- 
treme modification  in  most  of   the  other  regions.     Here 


OSTEOLOGY.  43 

we  see  the  ribs  running  downwards  from  tlie  lateral  parts 
of  the  body,  continued  by  the  sterno  -  costal  cartilages, 
between  which,  at  their  lower  extremities,  is  the  sternum  or 
hcemal  spine.  From  various  parts  of  the  arches  processes 
project ;  thus  at  the  anterior  and  posterior  extremity  of 
each  lamina  is  an  articular  or  oblique  process,  with  a  syno- 
vial facet  for  union  with  the  neighbouring  vertebrae,  A 
process  is  also  found  on  the  point  of  union  of  the  neural 
laminae  and  pedicles  which  generally  unites  with  another 
from  the  point  of  junction  of  the  pedicles  and  the  centrum, 
forming  the  transverse  processes  of  the  cervical  and  dorsal 
vertebrce.  The  lumbar  transverse  processes  consist  simply 
pf  the  inferior  process,  the  superior  in  this  region  being 
blended  with  the  anterior  oblique.  The  two  in  the  cervical 
region  are  distinct  at  their  commencement,  but  united  at 
their  free  extremities ;  thus  they  form,  the  vertebral  fora- 
mina. From  the  under  surface  of  the  centrum,  in  some 
parts,  a  process  arises  and  passes  in  a  downward  direction ; 
this  is  generally  termed  the  inferior  spinous  process. 

The  spinal  vertebrae,  as  a  rule,  present  the  centrum  with 
the  neural  arch  and  its  processes.  The  centrum  has  a 
flattened  superior  surface,  from  each  extremity  of  which 
triangular  roughened  surfaces  extend  towards  the  centre, 
where  their  apices  are  slightly  separated  by  a  smooth 
channel  which  connects  other  channels  situated  between 
the  roughened  surfaces  and  the  inferior  extremities  of  the 
laminae.  The  anterior  surface  of  the  body  is  convex,  and 
is  attached  by  means  of  a  disc  of  fibro-cartilage  to  the 
posterior  surface  of  the  vertebra  in  front,  which  is  corre- 
spondingly concave.  The  extremities  of  the  body  are  its 
widest  parts,  so  that  its  central  portion  is  smallest ;  it 
presents  two  surfaces  converging  to  form  a  prominent  line 
extending  from  before  backwards  along  the  under  surface. 
It  is  this  line  which,  in  some  cases,  forms  the  inferior 
spinous  process.  The  ring  or  arch  of  the  vertebra  is  formed 
by  the  lamince  and  pedicles ;  the  latter  present  grooves  on 
their  anterior  and  posterior  margins,  and  the  anterior 
groove  of  the  vertebra,  uniting  with  the  posterior  groove 
of  the  vertebra  in  front  of  it,  forms  an  intervertebral 
foramen  or  gap,  by  means  of  which  nerves  escape  from, 
and  vessels  pass  into,  the  spinal  canal.  The  vertebrae  of 
the  spinal  column  may  be  true  or  false,  the  true  vertebrae, 
or  those  which  are  capable  of  more  or  less  extensive  motion 


4-1  OUTLINES    OF    EQUINE    ANATOMY. 

upon  tlie  neiglibouring  vertebrae,  and  wliicTi  present  a 
regular  set  of  the  processes  of  the  neural  arch,  including 
spinous  (superior  and  inferior),  oblique  (anterior  and  pos- 
terior), transverse  (simple  or  compound).  True  vertebrae 
are  found  in  the  cervical,  dorsal,  and  lumbar  regions  ;  they 
do  not  all  present  all  the  processes  above  named,  but  their 
processes  present  a  certain  amount  of  regularity.  This 
is  different  in  the  coccygeal  vertebrae,  and  as  the  sacral 
bones  coalesce  the  vertebrae  in  these  two  regions  are  termed 
false.  The  distinction  between  true  and  false  vertebrae  is 
very  artificial.  The  vertebrae  in  these  different  regions 
present  peculiarities  which  are  distinctive,  but  it  will  be 
observed  that  the  characters  are  gradually  assumed  ;  thus, 
the  vertebrae  in  the  posterior  part  of  a  region  tend  to 
assume  the  figure  of  those  of  the  anterior  part  of  the  next. 
The  specific  characters  are,  therefore,  best  marked  in 
the  central  vertebrae  of  a  region.  We  shall,  therefore, 
describe  the  third  cervical,  ninth  dorsal,  and  third  lumbar 
vertebrae  as  typical  of  their  several  regions.  The  sacrum 
will  be  examined  as  a  whole,  the  coccygeal  vertebrae  will 
require  but  slight  notice. 


THIHD  CEHVIGAL  VEHTEBRA 

presents  a  regular  ring  and  set  of  processes.  The  body 
is  long,  enlarged  at  each  extremity.  The  anterior  extremity 
is  heart-shaped,  looks  downwards  and  forwards,  is  convex, 
and  has  its  base  superiorly  placed.  It  is  convex  in  all 
directions,  and  by  a  disc  of  cartilage  is  connected  to  the 
posterior  sarface  of  the  body  of  the  second  cervical  vertebrae. 
The  posterior  extremity  is  mainly  occupied  by  a  large  con- 
cave surface,  to  which  the  intervertebral  disc  is  attached. 
Its  margin  is  slightly  flat  superiorly,  and  it  looks  upwards 
and  backwards.  Its  outer  circumferent  margin  is  a  sharp 
ridge ;  its  upward  aspect  serves  to  prevent  dislocation 
downwards.  The  upper  surface  of  the  body  presents  the 
arrangement  already  noticed,  and  through  the  lateral  and  the 
transverse  grooves  run  venous  sinuses.  The  roughened  sur- 
faces are  for  attachment  of  the  superior  vertebral  ligament, 
and  are  large  in  corresponding  proportion  to  the  size  of  the 
body.  T\iQ  lateral  surfaces  of  the  body  are  somewhat  rough, 
and  converge  towards  the  central  line  of  the  inferior  part 
where  they  meet,  in  forming  a  ridge  extending  from  the  apex 


OSTEOLOGY.  45 

of  the  anterior  articular  surface,  to  a  roughened  tubercle 
situated  below  the  centre  of  the  posterior  articulatory 
surface.  This  is  the  inferior  spinous  processes,  and  to 
them,  as  well  as  to  the  lateral  surfaces,  which  are  slightly 
concave,  longiis  colli  is  attached.  The  pedicles  present 
the  superior  root  of  the  transverse  process  arising  from 
their  external  surface,  extending  obliquely  from  the  an- 
terior oblique  process  downwards  and  backwards.  The 
superior  spinous  process  arises  as  a  sharp  ridge,  becoming 
expanded,  rough,  and  blended  with  the  posterior  oblique 
processes  posteriorly  ;  to  it  are  attached  ligamentum  nuchse 
and  the  superior  spinous  ligament.  On  either  side  of  this 
the  superior  surface  of  the  laminae  is  concave  and  rough, 
anteriorly  presenting  a  groove  circumscribing  the  anterior 
oblique  process,  posteriorly  a  circular  line,  marking  the 
commencement  of  the  roughened  upper  surface  of  the  pos- 
terior oblique  process.  The  anterior,  and  posterior  margins 
of  the  laminae  between  the  oblique  processes  are  concave, 
and  afford  attachment  to  the  interlaminal  ligaments.  The 
oblique  processes  are  all  very  large,  present  extensive 
roughened  surfaces  for  muscular  attachment,  and  large 
circular  articulatory  surfaces.  The  anterior  articulatory 
facets  look  upwards  and  inwards,  and  are  slightly  convex, 
the  posterior  downwards  and  outwards,  and  are  slightly 
concave.  The  two  anterior  oblique  processes  are  connected 
by  the  above-mentioned  sharp  anterior  margin  of  the 
laminae,  the  posterior  processes  by  a  thick  concave  roughened 
line,  which  is  the  posterior  margin  of  the  laminse,  and 
serves  to  unite  two  roughened  prominences  separated  from 
the  articulatory  surfaces  by  a  slight  groove.  The  trans- 
verse processes  each  present  two  roots  separated  by  a 
canal,  through  which  the  vertebral  artery  vein  and  branch 
of  the  sympathetic  nerve  pass.  The  upper  root  is  derived 
from  the  outer  surface  of  the  pedicle  at  a  line  extending 
obliquely  from  its  antero- superior  to  its  postero-inferior 
angle.  The  other  root  commences  at  the  supero- lateral  part 
of  the  body  of  the  vertebra.  The  vertebral  canal  is  con- 
tinued backwards  to  the  posterior  part  of  the  body  by  a 
smooth  groove  ;  anteriorly  it  commences  at  a  funnel-shaped 
opening  just  behind  the  anterior  articulatory  surface.  The 
process  has  two  tubercles  on  its  free  margin,  both  of  which 
are  rough  and  tuberous.  The  anterior  extends  obliquely 
downwards  and  forwards,  the  posterior  runs  horizontally 


4Q  OUTLINES    OF    EQUINE    ANATOMY. 

backwards,  slightly  curled  upwards  at  its  roughened  free 
margin.  Both  of  these  tubercles  a^ord  attachment  to 
muscles.  The  inferior  surface  of  the  process  is  concave 
and  rough  ;  the  superior  surface  convex.  Its  anterior  margin 
is  concave,  smooth,  and  rounded ;  its  posterior  margin  con- 
cave and  sharj). 

CEEVICAL  VEETEBRJE 

in  general  are  remarkable  for  their  size,  for  the  large  size 
of  their  foramina  magna  and  intervertebral  gaps,  for  the 
regularity  and  uniform  length  of  their  processes,  and  for 
their  general  roughnesses,  and  the  facilities  they  afford  for 
muscular  attachment.  Each  of  them,  however,  presents 
modifications.  The  first  two,  atlas  and  dentata,  approxi- 
mate the  characters  of  the  vertebrae  which  are  modified 
to  form  the  skull ;  the  last  two  tend  to  assume  the  dorsal 
type.  The  third,  fourth,  and  fifth  are  with  difilculty  dis- 
tinguishable. The  following  modifications  will  he  observed  in 
examining  the  vertebroe  from  the  third  to  the  seventh. 

The  posterior  part  of  the  superior  spinous  processes 
becomes  more  separated  from  the  posterior  oblique  pro- 
cesses. The  anterior  and  posterior  oblique  processes  in 
the  third  are  separate,  in  fourth  united  by  a  thin  ridge, 
in  fifth  by  a  roughened  ridge.  The  concavity  between  the 
superior  spinous  process  and  the  anterior  oblique  processes 
becomes  more  and  more  marked  to  the  sixth.  The  articula- 
tory  surfaces  on  both  oblique  processes  increase  in  size  from 
before  backwards,  as  do  also  the  vertebral  foramina,  and 
the  articulatory  surfaces  gradually  change  from  the  vertical 
to  the  horizontal  position.  The  inferior  spinous  process 
decreases  in  size  to  the  sixth,  where  it  is  almost  imper- 
ceptible; it  becomes  larger  m  the  seventh  and  very  irregular. 
The  posterior  tubercle  from  before  backwards  manifests  a 
tendency  to  division,  which  in  the  sixth  is  very  marked,  so 
that  the  superior  and  inferior  parts  foim  distinct  promi- 
nences, of  which  the  superior  is  triangular,  concave  pos- 
teriorly. From  the  dentata  to  the  sixth  the  superior 
spinous  processes  decrease  in  size,  but  the  seventh  has  a 
broad  superior  spinous  process  terminating  superiorly  in 
a  point.  This  is  the  shortest  of  the  cervical  vertebrae.  Its 
transverse  process  is  square,  undivided,  and  has  only  one 
root.     Its  posterior  oblique  processes  present  much  smaller 


OSTEOLOGY.  47 

articulatory  surfaces  than  the  anterior,  but  not  the  smallest 
in  the  neck.  They  come  into  contact  with  the  anterior 
oblique  processes  of  the  first  dorsal  vertebra.  This  ver- 
tebra, at  the  supero-posterior  and  lateral  parts  of  the  body, 
has  a  concave  synovial  facet  on  each  side  for  the  head  of 
the  first  ribs.  The  first  and  second  cervical  vertebrae 
require  more  detailed  description. 

ATLAS  is  the  first  cervical  vertebra,  and  in  it  we  see  a 
manifestation  of  analogy  with  the  cephalic  vertebrae  in  the 
expansion  of  its  parts.  Its  ring  is  very  large,  ovoid  from 
side  to  side  anteriorly,  circular  posteriorly.  It  accommo- 
dates the  commencement  portion  of  the  spinal  cord  with 
its  membranes,  the  commencement  portion  of  the  basilar 
and  of  some  meningeal  arteries,  the  spinal  accessory  nerve, 
some  venous  sinuses  and  fat.  Also  posteriorly  the  odontoid 
process  of  the  dentata,  with  its  ligaments.  The  body  is  very 
small,  flattened  from  above  downwards.  Its  superior  sur- 
face anteriorly  has  a  roughened  groove,  extending  on  either 
side  outwards  and  backwards  for  attachment  of  the  odon- 
toid ligaments.  Posteriorly  it  presents  an  articulatory 
surface  concave  from  side  to  side,  surrounded  by  a  ridge, 
continuous  with  the  articulatory  surface  upon  the  posterior 
part  of  the  bone.  The  inferior  surface  is  convex.  Anteriorly 
it  has  the  lower  part  of  the  articulatory  surfaces  for  the 
condyles  of  the  occiput,  converging  inferiorly,  where  they 
are  separated  by  a  groove  to  which  their  synovial  mem- 
branes are  attached,  and  which  is  continuous  with  a  small 
triangular  space  on  the  antero -inferior  part,  which  is  occu- 
pied by  a  ligament.  At  the  postero-inferior  part  of  the 
body  is  a  prominence  looking  backwards,  tubercle  or  in- 
ferior spinous  process,  to  which  longus  colli  (and  the 
inferior  vertebral  ligament)  is  attached.  On  either  side  of 
this  the  bone  is  rough  for  attachment  of  obliquus  capitis 
anticus.  Opposite  the  articulatory  surfaces  it  is  convex 
and  bulging,  between  these  somewhat  concave  and  smooth. 
The  pedicles  run  obliquely  upwards  and  outwards  from  the 
lateral  parts  of  the  body  of  the  bone,  being  concave  and 
rough  internally,  convex  externally,  and  expanded  at  either 
extremity,  forming  those  portions  of  this  vertebra  which 
correspond  to  oblique  processes  of  others.  Anteriorly  the 
expanded  part  presents  an  articulatory  facet  for  union  with 
a  condyle  of  the  occiput.  It  superiorly  looks  downwards 
and  slightly  forwards,  running  outwards.    It  then  becomes 


48  OUTLINES    OF   EQUINE   ANATOMY. 

reflected  inwards  and  looks  upwards ;  inferiorly,  a  small 
portion  looks  directly  inwards  and  converges  tow^ards,  but 
does  not  quite  meet,  its  fellow.  Thus  we  have  formed  an 
irregular  cotyloid  cavity. 

The  posterior  expanded  portion  of  the  pedicle  presents  a 
convex  triangular  facet,  having  its  apex  at  the  postero- 
external angle  of  the  lamina  sharp  and  acute,  its  infero- 
external  angle  rounded,  its  infero-internal  angle  continuous 
with  the  smooth  postero- superior  part  of  the  body.  It 
looks  inwards  and  backwards,  and  comes  into  connection 
with  the  anterior  surface  of  the  body  and  with  the  odontoid 
process  of  the  dentata.  The  laminae  internally  are  concave 
and  rough  ;  exiernally  convex,  having  a  small  ridge  centrally 
at  the  anterior  part,  a  rounded  and  roughened  promi- 
nence for  attachment  of  the  superior  spinous  ligament  and 
rectus  capitis  posticus  minor  posteriorly.  The  anterior 
margin  is  a  sharp  ridge,  forming  a  concavity  affording 
attachment  to  the  capsular  and  lateral  ligaments  of  the 
attoido-occipital  joint,  extending  from  the  articular  surface 
for  one  condyle  to  that  for  the  other.  At  the  antero- 
external  angle  the  point  of  junction  of  the  lamina  and 
pedicles  is  pierced  by  a  foramen  extending  into  the  spinal 
canal,  continuous  with  one  in  the  anterior  part  of  the  wing. 
This  gives  passage  to  the  suboccipital  nerve,  and  to  a 
branch  of  artery  going  inwards  to  assist  in  forming  the 
basilar.  The  transverse  process  ala,  or  wing,  extends  from 
above  downwards  and  backwards,  obliquely  to  the  infero- 
external  angle  of  the  posterior  articular  surface.  It  is  a 
thin  plate  of  bone,  extending  downwards  and  outwards ; 
since  its  surfaces  are  concave  it  is  thinnest  at  its  centre,  and 
here  it  is  pierced  by  a  foramen  leading  from  a  groove,  through 
which  the  vertebral  artery  passes  from  above  downwards. 
Its  outer  margin  is  convex,  thick,  and  rough,  and  extends 
obliquely  downwards  and  outwards,  posteriorly  a  little 
behind  the  rest  of  the  bone  at  its  most  convex  part.  It 
affords  attachment  to  several  muscles  of  the  neck,  levator 
humeri,  splenius,  trachelo-mastoideus,  also  to  obliquus 
capitis  superior  and  obliquus  capitis  inferior.  In  the  con- 
cavity beneath  the  wing  the  union  of  the  vertebral  artery 
with  ramus  anastomoticus  takes  place,  and  the  resulting 
branch  passes  through  the  anterior  foramen,  thus  gaining 
the  superior  surface,  sending  one  branch  into  the  spinal 
canal,  the  other  to  the  poll.  The  superior  cervical  ganglion 


OSTEOLOGY.  49 

is  also  situated  in  tlie  concavity  of  tlie  under  surface  of  the 
wing. 

The  DENTATA  OR  AXIS  is  tlie  largest  and  tlie  longest 
of  the  true  vertebrae,  and  has  the  largest  superior  spinous 
process  ;  it  is  the  second  cervical  vertebra.  Its  body  is 
very  long,  but  superiorly  presents  the  usual  arrangement 
for  venous  sinuses  and  the  attachment  of  the  superior 
vertebral  ligament.  Anteriorly  it  presents  a  synovial  sur- 
face for  union  with  atlas,  and  centrally  the  odontoid 
process  :  superiorly  this  process  is  separated  from  the  rest 
of  the  upper  surface  of  the  body  by  a  rough  line  from 
which  another  runs  forward  to  the  anterior  margin.  The 
space  on  either  side  between  the  ridges  is  concave  ;  to  the- 
transverse  ridge  is  attached  the  broad,  to  the  concavities 
the  short  odontoid  ligaments.  The  anterior  margin  is 
convex,  the  lateral  margins  sharp  and  elevated.  Theinfero- 
lateral  surface  of  the  process  is  convex  and  articulatory,. 
coming  into  connection  with  the  postero-superior  part  o£ 
the  body  of  the  atlas.  It  is  most  prominent  at  the  centre 
of  the  posterior  part,  forming  a  small  tubercle.  It  is  con- 
tinued on  either  side  on  to  the  antero-extornal  part  of  the 
body  as  a  rounded  synovial  surface,  looking  obliquely 
upwards  and  outwards.  The  under  surface  of  the  body 
centrally  presents  a  prominent  ridge,  sharp  posteriorlyy 
roughened  anteriorly.  It  affords  attachment  to  longus  colli 
and  to  the  inferior  vertebral  ligament.  Anteriorly  it  does 
not  extend  as  far  as  the  odontoid  process,  from  which  it  is 
separated  by  a  groove,  which  extends  completely  round  the 
anterior  part,  affording  attachment  to  the  capsular'  liga- 
ment of  the  atlo-axoid  articulation,  separating  the  inferior 
spinous  ridge  from  the  outer  circumferent  margin  of  the 
anterior  articulatory'  surfaces,  which  here  cause  expansion 
of  the  bone.  Posteriorly  the  body  laterally  presents  tv/o  sur- 
faces, converging  towards  the  inferior  ridge  roughened  for 
attachment  of  longus  colli.  From  the  supero-lateral  part, 
of  the  body  the  transverse  processes  run  obliquely  upwards 
outwards,  and  backwards ;  they  have  two  roots,  a  broad 
concave  one,  inferiorly  separated  by  the  vertebral  foramen 
from  a  smaller  one  superiorly  situated.  This  process  is 
undivided  at  its  free  extremity.  The  pedicles  are  long  and 
high,  thus  rendering  the  foramen  magnum  longest  verti- 
cally ;  their  inner  surface  is  rough  and  concave,  their  outer 
roiicjli  and  straight.    The  posterior  margin  is  concave,  assist- 

4 


50  OUTLINES    OF    EQUINE    ANATOMY. 

ing  tlie  third  cervical  vertebra  to  form  an  intervertebral 
gap.  The  anterior  margin  is  very  deeiDlj  indented,  generally 
forming  a  large  foramen,  bounded  anteriorly  by  a  small 
thin  jn-ocess  of'bone  or  of  white  fibrous  tissue  ;  from  this  a 
smooth  broad  grove  runs  downwards  to  the  vertebral  fora- 
men ;   it  gives  exit  to  the  second  cervical  nerve,  and  also 
gives  passage  to  vessels.     The  ]josterior  surface  of  the  body 
and  the  oblique  processes  (of  which  there  are  but  two,  pos- 
teriorly placed)  resemble  those  of  the  following  cervical 
vertebrae  already  described.     The  laminaB  inferiorly  form 
the  superior  part  of  the  ring,  superiorly  are  wholly  occupied 
by  the  superior  spinous  process,  which  is  very  thick,  and 
from  before  backwards  increases  in  height,  thickness,  and 
roughness  of  its  superior  margin.     This  margin  <x?iferior% 
affords  attachment  to  rectus  capitis  posticus  major  and  to 
the  superior  spinous  ligament,  j)osteriorly  to  ligamentuni 
nuchte   and  complexus  minor.     It  bifurcates  posteriorly, 
and  its  divisions  blend  with  the  oblicpie  jn'ocesses.     To  the 
sides  of  this  process  obliquus  capitis  inferior  is  attached 
along  its  whole  length. 

THE  BOESAL  VERTEBR-ffi 

are  eighteen  in  number,  and  are  characterised  by  the  length 
of  their  superior  spinous  processes,  and  by  the  synovial 
articulatory  surfaces  on  the  supero -lateral  parts  of  their 
bodies  for  union  with  the  heads  of  the  ribs,  also  by  articu- 
latory surfaces  on  their  transverse  processes  for  union  with 
the  tubercles  of  the  ribs.  They  are  the  smallest  of  the  true 
vertebrae.  In  the  anterior  part  they  tend  to  assume  the 
cervical,  in  the  posterior  the  lumbar  type. 

NINTH  DOESAL  VERTEBRA. 

The  body,  on  the  upper  surface,  presents  the  usual 
arrangement.  Its  two  sides  present  superiorly  at  the 
anterior  and  posterior  parts  concave  synovial  facets,  ex- 
tending on  to  the  external  surfaces  of  the  pedicles.  The 
anterior  facet  looks  forAvards  and  outwards,  and  comes  into 
connection  with  the  posterior  facet  of  the  rib  in  front.  The 
posterior  facet  looks  backwards,  and  slightly  outwards,  ana 
is  for  the  anterior  facet  of  the  head  of  the  rib  behind. 
■   Below  this  the  sides  are  concave  from  before  backwards, 


OSTEOLOGY.  51 

and  meet  inferiorly  in  forming  a  median  ridge  (wliicli  in 
some  of  the  vertebrae  of  tlie  dorsal  region  is  elongated  to 
form  tlie  inferior  spinous  process).  Eacli  of  the  sides  at  its 
centre,  though  inclined  to  the  anterior  part,  presents  a 
medullary  foramen,  through  which  a  branch  of  the  inter- 
costal artery  passes.  The  under  surface  of  the  bodies  of  the 
anterior  six  dorsal  vertebrae  is  covered  by  longus  colli,  of 
the  posterior  three  by  psose  parvi,  of  the  central  ones  by  the 
vena  azygos  on  the  right  side,  thoracic  duct  centrally, 
posterior  aorta  on  the  left.  The  anterior  surface  is  convex 
and  circular,  somewhat  flattened  superiorly.  It  gives 
attachment  to  the  intervertebral  disc,  and  is  adaj)ted  to 
the  posterior  surface  of  the  body  of  the  vertebra  imme- 
diately in  front  of  it.  The  posterior  surface  is  correspond- 
ingly concave.  The  pedicles  are  internally  smooth  and 
concave,  externally  rough,  slightly  encroached  upon  by  the 
facets  for  the  heads  of  the  ribs.  Anteriorly  and  posteriorly 
they  have  grooves  for  the  intervertebral  gaps  scarcely  per- 
ceptible anteriorly,  posteriorly,  in  some  cases,  converted 
into  a  foramen.  Centrally,  at  the  point  of  junction  with 
the  lamina,  is  a  tuberous  process,  rough  for  muscular 
attachment  (of  longissimus  dorsi  and  levatores  cos- 
tarum).  This  is  the  transverse  process,  and  has  on  its 
external  surface  a  small  irregular  convex  synovial  facet  for 
the  tubercle  of  the  rib,  having  between  it  and  the  posterior 
facet  on  the  body  a  smooth  groove,  extending  from  the 
intervertebral  gap.  The  laminae  are  concave  inferiorly, 
forming  the  roof  of  foramen  magmini,  supero-posteriorly, 
wholly  occupied  by  the  superior  spinous  process,  supero- 
anteriorly  presenting  a  small  synovial  facet  od  each  side, 
representing  the  anterior  oblique  processes ;  the  posterior 
oblique  processes  are  on  the  postero-inferior  part.  The 
superior  spinous  process,  remarkable  for  its  length,  runs 
obhquely  upwards  and  backwards.  Superiorly  it  is  tuberous, 
affording  attachment  to  the  superior  spinous  ligament,  and 
so  indirectly  to  muscles.  Its  anterior  margin  is  sharp, 
especially  inferiorly,  affording  attachment  to  the  inter- 
spinous  ligament.  It  is  much  longer  than  the  posterior 
margin,  which  is  centrally  sharp,  having  on  either  side 
a  groove,  deepest  inferiorly,  bounded  externally  by  a 
roughened  margin.  They  terminate  just  above  the  pos- 
terior oblique  processes.  The  central  sharp  ridge  bifurcates 
inferiorly,  one  division  running  to  each  oblique  process. 


52  OUTLINES    OF    EQUINE    ANATOMY. 

To  fhis   margin  also   is   attached   the  interspinous  liga- 
ment. 

Deferences  in  the  Dorsal  Vertebrae. 

Superior  spinous  jrrocesses  increase  in  length  to  fifth,  then 
decrease  to  thirteenth,  the  rest  being  about  uniform  ;  they 
are  inclined  backwards  to  the  sixteenth,  which  is  upright  ;- 
the  seventeenth  and  eighteenth  incline  slightly  forwards. 
First  comes  to  a  point  superiorly  ;  the  rest  increase  in  rough- 
ness and  thickness  to  the  sixth,  and  in  width  from  before 
backwards  in  the  twelve  posterior  vertebrae,  in  which  also' 
may  be  noticed  a  concavity  just  below  the  anterior  part  of  the 
superior  extremity.  In  the  central  vertebrae  the  anterior 
margin  is  rough  about  at  its  middle.  The  transverse  p-o- 
cesses  are  large  and  mainly  articulatory  in  the  first,  and  gra- 
dually become  modified  in  the  last  until  each  of  them  con- 
sists of  two  portions,  the  superior  of  which  is  blended  mth 
the  anterior  oblique  process,  the  inferior,  articulatory,  con- 
tinuous with  the  anterior  facet  on  the  lateral  part  of  the 
body  of  the  vertebra  in  the  case  of  the  last  two.  The 
articulatory  facets  for  the  heads  of  the  ribs  gradually  decrease 
in  depth  from  before  backwards.  The  intervertehral  notches' 
on  the  ijosterior  part  of  the  pedicles  are  in  the  fourth  to  the 
sixteenth  vertebrae  converted  into  foramina ;  hence  the  fifth 
to  the  seventeenth  have  no  anterior  notches.  The  articu- 
atory  surfaces  on  the  anterior  ohlique  processes  are  larger  than 
those  on  the  posterior.  The  former  look  outwards,  the 
latter  inwards  ;  their  tendency  in  this  is  increased  from 
before  backwards.  The  ohlique  processes  of  the  first  four 
vertebrae  are  distinct ;  in  the  other  vertebrae  the  articular 
surfaces  are  continued  on  to  the  laminae.  Inferior  spinous 
processes  are  marked  only  in  the  six  anterior  and  three  pos- 
terior vertebrae.  The  foramina  magna  are  largest  m  the 
anterior,  smallest  in  the  central^  vertebrae.  The  smooth 
grooves  on  the  iipper  surface  of  the  body  are  most  marked 
anteriorly.  The  last  dorsal  vertebra  has  no  posterior  arti- 
culatory surfaces  for  the  heads  of  the  ribs,  and  its  anterior 
surfaces  are  blended  with  those  of  its  transverse  processes. 

THE   LUMBAR  VERTEBRA 

are  the  vertebrae  forming  the  basement  structure  of  the 
loins,,  situated  between  the  dorsal  and  the  sacral  regions. 


OSTEOLOGY.  53 

In  general  characters  tliey  resemble  tlie  dorsal  vertebrae ; 
we  shall,  therefore,  only  notice  their  peculiarities.  These 
vertebrre  are  five  or  six  in  number,  are  larger  than  the 
dorsal,  and  each  presents  a  large  foramen  magnum  and 
transverse  processes ;  also  has  no  articulatory  surfaces  for 
the  heads  of  the  ribs.  The  superior  spinous  processes 
resemble  those  of  the  posterior  dorsal ;  all  look  forwards  ; 
are-  short  and  stout,  elongated  from  above  downwards, 
tuberous  at  their  upper  extremities,  anteriorly  presenting  a 
sharp  margin,  posteriorly  a  double  margin,  both  for  attach- 
ment of  the  interspinous  ligaments.  The  oblique  processes 
tend  to  assume  a  peculiar  rounded  hinge-like  character; 
those  on  the  posterior  part  present  a  rounded  convexity, 
elongated  from  behind  forwards,  looking  outwards  and 
'  downwards .  The  anterior  ohlique  pirocesses  have  articulatory 
surfaces  looking  upwards  and  inwards.  The  intervertebral 
gaps  are  large,  the  transverse  processes,  formed  by  a  single 
root,  extend  directly  outwards,  those  of  the  anterior  ver- 
tebrae having  a  slight  inclination  backwards,  those  of  the 
posterior  forwards.  Their  length  is  characteristic  of  the 
vertebrae  of  this  region.  They  are  flattened  from  above 
downwards,  and  of  the  first  five  vertebrae  are  tuberous  at 
their  free  extremities,  affording  attachment  to  quadratus 
lumborum,  psoas  magnus,  and  indirectly  to  some  of  the 
.abdominal  muscles. 

The  anterior  and  posterior  margins  are  sharp,  affording 
.attachment to  intertransversales  lumborum  ;  the  upper  and 
under  surf  axes  are  smooth  ;  the  former  affords  attachment 
to  longissimus  dorsi,  which  occupies  the  space  between 
this  and  the  superior  spinous  process ;  the  latter  to  the 
ipsoae  muscles.  When  six  lumbar  vertebrae  exist  the  trans- 
verse process  of  the  sixth  is  much  shorter  than  the  rest, 
.and  presents  articular  synovial  facets^hoth  on  its  anterior  and 
its  posterior  margins,  ovoid  and  elongated  from  side  to  side, 
separated  by  grooves  from  the  amphiarthrodial  facets  of 
the  body.  These  present  special  ligaments,  and  the  poste- 
rior one  slants  from  without  inwards  and  backwards,  being 
in  connection  with  the  first  sacral  transverse  process. 
The  anterior  slopes  in  a  similar  direction,  articulating 
vwith  a  corresponding  facet  on  the  posterior  part  of 
rthe  fifth  lumbar  transverse  process.  The  latter,  where 
there  are  only  five  lumbar  vertebrae,  is  modified  to  join  the 
.sacrum.     Most  horses  present  six,  most  asses  five,  lumbar 


54  OUTLINES    OF   EQUINE   ANATOMY. 

vertebrae.  The  bodies  of  tbese  vertebrae  are  larger  and 
more  prisuiatic  than  those  of  the  dorsal,  terminating  iiife- 
riorly  in  somewhat  marked  ridges,  inferior  spinous  pro- 
cesses, for  attachment  of  the  inferior  vertebral  ligament,  to 
which  the  crura  of  the  diaphragm  are  attached.  To  their 
lateral  surfaces]  the  psose  parvi  muscles  are  attached;  their 
anterior  and  posterior  surfaces  present  but  shallow  concavi- 
ties and  convexities.  The  bodies  and  foramina  magna 
decrease  in  height  from  before  backwards  ;  so  at  the  poste- 
rior part  of  the  last  lumbar  the  body  presents  a  shallow 
surface,  very  much  elongated  transversely. 


THE  SACRUM 


in  early  life,  consists  of  five  distinct  vertebrae,  which  in  the 
adult  become  firmly  united  by  healthy  bony  union,  whereby 
a  firm  basis  for  attachment  of  the  hind  limb  is  afforded. 
We  therefore  shall  view  it  as  a  single  bone,  since  it  acts  as 
such.  It  is  situated  at  the  j^osterior  part  of  the  spinal 
column,  between  the  lumbar  and  coccygeal  vertebrae.  It 
articulates  laterally  with  the  venter  ilii.  It  is  pyramidal 
in  figure,  its  base  being  anteriorly  placed  ;  sometimes  it  is 
composed  of  six  bones,  in  consequence  of  coalescence  of  the 
first  coccygeal  vertebra  with  its  ajjex.  It  is  a  false  ver- 
tebra, as  its  segments  are  not  capable  of  moving  upon  each 
other.  The  base  presents  laterally  foramen  magnum  coming 
to  a  point  superiorly  at  the  root  of  the  superior  spinous 
process,  broad  inferiorly.  It  leads  mto  a  canal  which 
gradually  and  regularly  decreases  in  size  from  before  back- 
wards, being  extremely  small  posteriorly.  The  spinal  cord 
extends  into  this  about  as  far  as  opposite  the  second  sacral 
bone ;  the  membranes  of  the  cord  are  continued  farther. 
Below  this  opening  is  an  articulatory  surface,  the  transverse 
diameter  of  which  is  about  twice  as  long  as  the  vertical ;  it 
is  slightly  convex  in  all  directions.  At  the  sui3ero -lateral 
parts  of  the  foramen  are  the  oblique  processes,  which  are 
roughened  externally,  and  internally  present  concave  facets 
looking  uj^wards  and  inwards.  From  the  inferior  part  of 
the  anterior  margin  of  each  of  these  a  thin  ridge  runs  to 
meet  its  fellow  at  the  root  of  the  superior  sj^inous  j^rocess 
of  the  first  bone.  Below  the  oblique  processes  are  the 
intervertebral  notches,  which  lead  into  grooves  running 
from  the  upper  to  the  under  surface  of  the  transverse  pro- 


OSTEOLOGY.  55 

cess  of  tlie  first  bone,  separating  the  articulatory  surface  of 
the  body  from  those  on  the  anterior  margins  of  the  transverse 
processes,  wliicli  overhang  the  grooves  inferiorly  in  a  re- 
markable manner.  These  surfaces  come  into  contact  with 
those  on  the  posterior  margin  of  the  transverse  processes 
of  the  last  lumbar,  of  which  they  are  the  exact  counterparts, 
being  almost  flat,  looking  inwards  and  slightly  upwards. 
They  extend  to  the  outei'  extremity  of  this  transverse  pro- 
cess, which  is  sharp,  and  at  its  superior  surface  form 
angles  with  rounded  roughened  surfaces  which  extend  to  the 
extremity  on  the  postero-external  part,  much  expanded, 
looking  upwards,  backwards,  and  outwards,  for  union  with 
the  venter  surface  of  the  ilium.  They  do  not  occupy  the 
whole  of  the  upper  surface,  but  are  continued  by  a  rough- 
ened ridge,  which  extends  along  the  lateral  part  of  the 
bone,  becoming  smaller  and  sharper  posteriorly,  formed  by 
union  of  the  transverse  processes  of  the  other  sacral  bones  ; 
it  affords  attachment  to  the  sacro-sciatic  ligament.  Both 
above  and  below  this  ridge  is  a  series  of  foramina,  four  in 
number,  decreasing  in  size  from  before  backwards  for 
passage  of  the  branches  of  the  sacral  nerves,  the  superior 
branches  through  the  superior  foramina,  the  inferior 
branches  through  the  inferior  foramina,  through  which 
also  pass  branches  of  the  lateral  sacral  arteries  and  veins. 
Above  the  superior  foramina  (supersacral)  are  a  series  of 
small  prominences,  decreasing  in  size  from  before  back- 
wards, produced  by  the  oblique  processes  of  the  bones. 
Higher  up  are  the  superior  spinous  processes,  more  or  less 
completely  united  by  ossification  of  the  interspinous  and 
interlaminal  ligaments,  presenting  a  series  of  five  tuberous 
prominences,  to  which  triceps  abductor  femoris,  biceps 
rotator  tibialis,  ischio -tibialis,  and  some  of  the  coccygeal 
muscles,  also  the  lateral  sacral  ligament  and  longissimus 
dorsi  are  attached.  The  first  spinous  process  looks  almost 
directly  upwards  ;  the  rest  have  a  marked  direction  back- 
wards, and  decrease  in  length  posteriorly.  The  inferior 
surface  of  the  bone  anteriorly,  on  either  side,  presents  a 
remarkable  smooth,  irregular  concavity,  being  the  under 
surface  of  the  transverse  process  ;  a  rounded  neck,  extend- 
ing inwards  and  backwards,  serves  to  unite  this  to  the 
main  portion,  which  is  formed  by  the  under  surfaces  of 
the  bodies,  as  denoted  by  transverse,  irregular  ridges, 
which  serve  to  divide  this  portion  into  five  flattened  parts. 


56  OUTLINES    OF    EQUINE    ANATOMY. 

It  is  slightly  concave  from  before  backwards,  is  widest 
anteriorly,  and  decreases  in  size  posteriorly  ;  on  either  side 
it  slopes  upwards  and  outwards,  presenting  the  inferior  roiv 
cf  foramina  (subsacral),  which  are  much  larger  than  the 
.superior.  Internally  placed  to  the  foramina  the  lateral 
sacral,  arteries  run  along  this  portion  of  the  bone.  The 
apex  consists  of  a  somewhat  rounded  and  slightly  concave 
.articular  surface,  surmounted  by  a  small  ring,  presenting  on 
either  side  a  small  transverse,  superiorlj^  a  superior  spinous 
process.     It  articulates  with  the  first  coccygeal  vertebra. 


THE  COCCYGEAL  VERTEBRiS 


from  thirteen  to  eighteen  in  number,  occupy  the  pos- 
jterior  part  of  the  vertebral  column,  and  are  small 
bones  in  which  the  different  parts  of  a  vertebra  assume  a 
more  and  more  rudimentary  form  from  before  backwards, 
so  that  while  the  first  presents  a  body,  ring,  and  small 
2)rocesses,  the  sixth  presents  only  a  body  with  two  pedicles 
and  small  transverse  processes  ;  the  posterior  coccygeal  hones 
..are  merely  small  bony  masses,  elongated  from  before  back- 
wards, enlarged  at  each  extremity,  where  they  become 
united  with  their  fellows  by  fibro- cartilage.  The  pos- 
terior bones  only  become  ossified  late  in  life,  so  that  the 
number  of  these  vertebrae  varies  with  age.  They  all 
present  both  anteriorly  and  posteriorly  convex  articulatory 
surfaces  to  their  bodies.  In  consequence  of  this,  mobility 
of  the  vertebral  column  here  attains  its  maximum,  but  the 
want  of  a  regular  set  of  processes  renders  these  false 
Tertebrse ;  superiorly  they  afford  attachment  to  the 
levatores  coccygis  ;  inferiorly  to  the  clepressores  ;  laterally 
to  the  curvatores.  The  anterior  bones  also  afford  attach- 
ment to  ischio-tibialis  and  to  compressor  coccygis. 

THE  RIBS,  COST^, 

together  with  the  sternum  and  the  cartilages  of  elongation 
.form  the  haemal  arch  of  the  dorsal  vertebral  segments. 
They  are  elongated  bones,  extending  from  above  down- 
wards from  the  lateral  parts  of  the  dorsal  vertebrae. 
Though  they  have  a  longitudinal  axis  greatly  exceeding 
either  of  the  transverse  axes,  yet  as  they  present  no  medul- 
lary canal  nor  marked  distinction  of  shaft  and  extremities, 


OSTEOLOGY.  57 

they  are   not  included  in  the  class  "  long  round  bones." 
Each  rib  presents  a  body  and  an  upper  extremity.     The 
extremity  is  divided  into  head,  connected  to  the  rest  of  the 
bone  by  the  nech,  and  tubercle.    The  head  is  a  more  or  less 
spherical  process,  with  two  convex,  synovial,  articulatory 
surfaces,  separated  by  a  roughened  groove.     The  anterior 
surface  articulates  with  the  posterior  facet  on  the  body 
of-  the  vertebra  in  front ;  the  posterior,  with  the  anterior 
facet  of  the  vertebra  behind  ;  the  groove  corresponds  to  the 
intervertebral  disc  of  cartilage  and  affords  attachment  to 
ligamentum  teres.     Around  each  of  the  articulatory  sur- 
faces is  a  slight  groove  for  attachment  of  a  capsular  liga- 
ment.    In   the   two   last   ribs   the   posterior   articulatory 
surface  is  continuous  with  the  facet  of  the  tubercle.     The 
neck  varies  in  thickness  and  rotundity  in  the  different 
ribs  ;  its  inner  surface  is  roughened  for  attachment  of  the 
stellate  ligament.     The  tubercle  seems  to  be  the  superior 
part  of  the  body,  and  is  posteriorly  placed  to  the  head. 
That  of  the  first  rib  is  largest ;  it  gradually  decreases  in 
size  in  the  bones  from  before  backwards,  so  that  it  is  ex- 
tremely small  in  the  two  last.     From  this  process  arises 
levator  costse,  and  to  it  is  attached  longissimus  dorsi.     It 
presents  on  its  internal  surface,  becoming  more  anteriorly 
placed  in  the  posterior  vertebras,  a  small  articulatory  facet 
for  union  with  the  transverse  process  of  the  dorsal  verte- 
brae ;  the  outer  circumferent  margin  of  this  is  rough  for 
attachment  of  the  capsular  ligament,  and  on  either  side 
for  the  costo-trans verse  ligaments.     The  body  is  more  or 
less  flattened  irregularly  from  without  inwards,  and  in  the 
central  ribs  is  so  twisted  upon  itself  that  the  two  extremi- 
ties will  not  rest  upon  a  plane  surface  at  the  same  time. 
The  eighth  rib  takes  the  following  course  from  its  upper 
extremity  :  at  first,  outwards,  backwards,  and  downwards  ; 
centrally,   more   directly   downwards ;   inferiorly   slightly 
inwards  and  backwards.     The  body  therefore  presents  two 
margins  and  two  surfaces.     The  internal  surf  ace  is  smooth, 
convex  from  before  backwards,  concave  from  above  down- 
wards.    It  is  covered  by  the  pleura  costalis,  through  which 
it  may  be  seen  on  laying  open  the  thorax  of  a  fresh  sub- 
ject.    At  its  extreme  superior  part  the  sympathetic  gan- 
-gliated  cord  may  be  seen.     To  the  extreme  inferior  part  of 
this  surface  of  the  posterior  ribs  are  attached  the  diaphragm 
.and  transversalis  abdominis.  The  external  surface  is  convex 


58  OUTLINES    OF    EQUINE    ANATOMY. 

ill  all  directions  ;  in  the  anterior  ribs  its  lower  part  affords 
attacliment  to  serratus  magnns,  in  tlie  fourteen  posterior 
ribs  to  obliquus  abdominis  externus,  in  the  four  or  five 
posterior  ribs  to  obliquus  abdominis  internus.     To  about 
the  inferior  part  of  the  superior  third  of  the  last  two  ribs 
a  line  of  prominences  extend,  one  on  each  rib,  from  the 
tubercle  of  the  second  ;   to  this  transversalis  costarum   is 
attached,  while  a  corresponding  superior  line  of  promi- 
nences runs  from  the  fourth  tubercle  to  meet  the  former  in 
the  sixteenth  rib  ;  it  marks  out  the  inferior  limit  of  longis- 
simus  dorsi,  and  opposite  to  it  the  bone  makes  its  most 
marked  curve  downwards,  which  is  termed  the  angle  of 
the  rib.      Superficialis  costarum  is   attached  below   the 
inferior  row  of  prominences.     The  anterior  margin  affords 
attachment  to  the  intercostales  externi  at  its  outer  edge, 
superiorly  to  levatores  costarum,  at  its  inner  edge  to  inter- 
costales interni.     In  the  fourteenth  rib  a  small  groove  runs 
along  this  margin  from  the  head  of  the  bone  ;  it  gradually 
increases  in  length  in  the  ribs  in  front  of  this,  so  that  in 
the  second,  third,  and  fourth  the  external  margin  seems 
bevelled   off  from    behind   forwards,  affording   extensive 
surface  for  attachment.     The  posterior  margin  presents  a 
corresponding  arrangement  on  the  inner  side.     It  affords 
attachment  to  the  intercostales  in  a  similar  manner  to  the 
anterior  margin.     Towards  their  inferior  extremities  the 
ribs  tend  to  become  rounded,  the  ninth  being  most  so. 
The  posterior  ribs  assume  the  character  of  thin  long  bones 
composed   of   two   rounded   surfaces    meeting    by   sharp 
margins.     They  increase  in  width  from  before  backwards 
to  the  sixth,  after  which  they  decrease.     In  length  they 
decrease  from  the  eighth  both  backwards  and  forwards, 
the  first  being  the  shortest.     The  inferior  extremity  of  the 
body  is  continuous  with  the  cartilage  of  elongation,  the 
union  being  more  or  less  gomphotic.     The  cartilage  has  a 
considerable  tendency  to   undergo   ossification,   thus   as- 
suming the  normal  character  of  the  inferior  costa  as  found  in 
birds  ;  the  bone  therefore  extends  downwards  in  the  centre 
of  the  cartilage  to  a  degree  varying  with  the  age  of  the 
animals.     Some  of  these  cartilages  are  directly  attached 
to   the  sternum,   others   indirectly  through   the   medium 
of  their  fellows.     Those  of  the  first  class  belong  to  the 
first  eight  ribs,  which  therefore  are  said  to  be  true  ribs, 
behind  these,  on  each  side,  are  generally  ten  false  ribs^ 


OSTEOLOGY.  59 

sometimes  nine  or  eleven,  with  tlie  inferior  extremity  of 
tlie  cartilage  pointed,  and  more  or  less  firmly  united  to  the 
neighbouring  cartilages  by  a  small  elastic  ligament.  The 
union  of  the  posterior  cartilages  is  most  lax,  and  in  some 
cases  the  last  rib  is  wholly  unconnected  to  the  last  but  one ; 
it  is  then  said  to  be  floating.  The  floating  rib  is  generally 
found  when  nineteen  ribs  exist  on  each  side ;  sometimes  it 
is  -a  mere  cartilaginous  elongated  body  extending  from  the 
transverse  process  of  the  first  lumbar  vertebra  imbedded 
in  the  abdominal  muscles.  The  external  surface  of  the 
fourteen  posterior  cartilages  is  connected  with  the  external 
oblique  abdominal  muscle.  To  that  of  the  four  or  five 
jDOsterior  true  ribs  rectus  abdominis  is  attached,  and  ante- 
riorly is  blended  with  lateralis  sterni,  which  is  continued 
obliquely  forwards  and  upwards  over  the  second  and  third 
to  become  attached  to  the  first,  from  which  also  sterno- 
thyro-hyoideus  partly  derives  its  inferior  attachment.  The 
cartilages  decrease  in  thickness  from  before  backwards ; 
they  increase  in  length  from  behind  and  from  before  to 
the  ninth  and  tenth.  They  are  connected  together  by  the 
inferior  thickened  portion  of  the  intercostales  interni,  for 
the  external  intercostales  terminate  opposite  the  inferior 
extremity  of  the  rib.  The  inferior  extremity  of  the 
cartilages  of  the  false  and  floating  ribs  terminates  in  a 
point,  that  of  the  true  ribs  is  convex,  coated  with  ar- 
ticular cartilage,  articulating  with  the  cartilage  of  the 
sternum. 

The  first  rib  is  the  shortest  and  strongest,  and  is  also 
the  straightest.  Its  head  articulates  with  the  last  cervical 
and  first  dorsal  vertebrae.  Its  tuhercle  is  large  and  very 
rough  externally  for  attachment  of  transversalis  costarum, 
and  longissimus  dorsi.  It  is  irregularly  rounded,  to  the 
inner  surface  is  attached  the  pleura  at  its  reflection  to 
form  the  mediastinum.  And  many  of  the  important 
structures  which  pass  through  the  entrance  of  the  thorax 
lie  in  contact  with  this  bone.  The  posterior  margin 
affords  attachment  to  the  first  intercostals.  The  ante- 
rior margin  presents  at  the  inferior  part  of  the  superior 
third,  a  prominence  to  which  the  short  or  upper  head 
of  scalenius  is  attached.  Below  this  the  bone  is  smooth 
for  the  passage  of  the  axillary  plexus  of  nerves.  On 
the  external  surface  at  the  superior  part  of  the  inferior 
third    the    lower  head   of    scalenius    is    attached,    and 


-GO  OUTLINES    OF    EQUINE    ANATOMY. 

under  it  are  two  smooth  grooves  for  tlie  passage  of  the 
axillary  artery,  and  (below  it)  the  axillary  vein.  The  rest 
of  this  surface  is  occupied  by  the  attachuient  of  serratus 
magnus.  The  cartilage  of  the  first  rib  is  the  shortest  and 
stoutest,  and  very  closely  approximates  its  fellow  of  the 
■opposite  side. 

The  last  rib  is  the  smallest,  and  its  ])osterior  margi7i 
gives  attachment  to  quadratus  lumborum.  To  the  inner 
surface  of  the  last  two  ribs  the  psoas  magnus  attached. 
We  have  seen  that  the  anterior  ribs  are  strongest,  broadest, 
and  most  firmly  connected  together  ;  they  are  thus  admir- 
ably adapted  to  the  formation  of  the  thorax,  which  not 
only  serves  to  protect  important  viscera,  but  also  affords 
an  extensive  base  for  attachment  of  the  fore  limbs  to  the 
trunk.  This  cavity  is  completed  below  by  the  STERNUM, 
which  consists  of  "^the  haemal  spines  of  six  vertebral  seg- 
ments embedded  in  a  cartilaginous  mass,  so  that  they  may 
be  viewed  as  one  bone.  Each  of  these  bones  presents 
seven  surfaces.  The  superior  surface  is  smooth,  forms  the 
floor  of  the  thorax,  where  it  gives  attachment  to  ligaments, 
and  to  the  sterno-costales  interni.  That  of  the  sixth  bone 
on  either  side  presents  the  articulatory  surfaces  for  the 
cartilages  of  the  last  two  true  ribs,  of  the  fifth  bone  for 
the  sixth  sterno-costal  cartilage.  ThQ  anterior  im^ posterior 
surfaces  are  rough  for  attachment  of  the  cartilage,  while 
the  superior  and  inferior  lateral  surfaces,  scarcely  distin- 
guishable in  the  first  bone,  assist  in  forming  the  lateral 
and  inferior  surfaces  of  the  bone  taken  as  a  whole.  These 
bones  decrease  in  depth  and  increase  in  width  from  before 
backwards.  They  are  prolonged  anteriorly  and  posteriorly 
by  cartilages.  The  anterior  cartilage  i^resents  a  rounded 
supero-anterior  extremity  from  which  a  short  concave 
superior  margin  runs  to  the  antero- superior  part  of  the 
first  bone.  An  inferior  margin  convex,  rounded  smooth 
along  the  central  line  of  the  under  surface,  blending  with 
the  inferior  margins  of  the  bone  almost  as  far  backwards 
as  the  posterior  cartilage.  It  is  flattened  from  side  to  side, 
though  growing  broader  posteriorly,  and  thus  it  gives 
the  sternum  a  keel-shape  ;  it  is  the  cariniform  cartilage. 
Its  prominent  antero-superior  part  would  form  the  prow. 
The  ensiform,  posterior  or  xiphoid  cartilage  is  a  mem- 
braniform  piece  of  cartilage,  flattened  from  above  down- 
wards, widest  at  its  attachment  to  the  posterior  part  of 


OSTEOLOGY.  61 

the  last  bone,  decreasing  in  size  posteriorly  to  form  tlie 
neck,  subsequently  again  expanded  in  forming  an  aiypendix 
portion.  To  its  under  surface  are  attached  the  abdominal 
oblique  and  rectus  muscles,  also  pectoralis  magnus,  to  the 
upper  surface  the  diaphragm  and  trans versalis  abdominis 
and  the  fibrous  pericardium.  The  sternum  thus  presents  three 
surfaces  and  two  extremities.  The  anterior  extremity  is  the 
prow  of  the  carinif  orm  cartilage ;  to  it  sterno-maxillaris 
and  sterno-thyro-hyoideus  are  attached.  The  jjosfer /or  ex- 
tremity is  formed  by  the  ensiform  cartilage.  The  lateral 
surfaces  anteriorly  give  attachment  to  pectoralis  anticus, 
posteriorly  to  pectoralis  magnus  and  trausversus.  The 
inferior  margin  is  anteriorly  smooth  and  rounded  ;  it  here 
presents  a  spurious  bursa,  over  which  pectoralis  traus- 
versus plays.  The  tipper  surface  is  slightly  concave,  both, 
longitudinally  and  transversely.  Centrally  it  affords  at- 
tachment to  the  mediastinum.  Anteriorly  the  thymus 
gland  rests  on  it,  posteriorly  the  fibrous  pericardium  is 
attached.  Laterally  it  presents  the  articulatory  surfaces 
for  the  inferior  extremities  of  the  sterno-costal  cartilages, 
and  internally  placed  to  this  the  internal  thoracic  artery 
runs  from  before  backwards,  with  its  accompanying  vein. 
The  first- sterno-costal  cartilage  articulates  with  the  sternum 
just  in  front  of  the  first  bone,  the  second,  third,  fourth, 
and  fifth  with  the  intervals  between  the  following  bones, 
the  sixth  with  the  fifth  bone,  the  seventh  and  eighth  witk 
the  last. 

BONES  OF  THE  FORE  LIMB. 

The  SCAPULA  is  a  flat  triangular  bone,  placed  on  the 
antero-lateral  part  of  the  thorax,  having  its  apex  inferiorly 
opposite  the  first  rib,  its  base  extending  oblicjuely  down- 
wards as  far  as  the  angle  of  the  sixth  rib.  A.  fiat  bone  is 
required  in  this  position  to  aftbrd  sufficient  surface  for 
attachment  of  the  large  muscles  which  connect  the  fore 
limb  to  the  trunk,  for  in  the  horse  two  bones  (coracoid  and 
clavicle)  which  perform  this  function  in  many  other  animals 
are  rudimentary.  It  presents  two  surfaces,  three  borders, 
and  three  angles.  The  anterior  border  is  superiorly  convex 
and  roughened,  inferiorly  concave  and  smooth,  and  at  its 
extreme  inferior  part  presents  a  large  roughened  process, 
coracoid  (a  rudiment  of  a  distinct  bone).  This  process 
externally  presents,  superiorly  a  groove  for  a  blood-vessel 


62  OUTLI^ES    OF    EQUINE    ANATOMY. 

running  obliquely  downwards  and  backwards ;  below,  and 
almost  parallel  to  this  a  roughened  ridge,  mapping  out  tlie 
line  of  attachment  of  flexor  brachii,  may  be  traced  in  a  cir- 
cular manner  around  the  whole  anterior  part  of  the  process. 
On  the  inner  surface  is  a  ridge  with  a  slight  inclination 
backwards,  terminating  inferiorly  in  a  small  process  to  which 
coraco-humeralis  is  attached.  Around  the  anterior  margin 
of  the  bone,  just  above  the  coracoid  process,  runs  arteria 
dorsalis  scapulae  with  its  accompanying  vein  and  nerve 
from  within  outwards,  protected  by  a  hand  of  white  fibrous 
tissue  {cor aco- scapular  ligament),  which  extends  from  the 
process  to  about  the  middle  of  this  margin  of  the  bone ; 
antea  spinatus  becomes  attached  to  this  ligament  exter- 
nally; subscapularis  internally.  The  roughened  anterior 
margin  at  its  superior  part  affords  attachment  to  pectoralis 
anticus  and  antea  spinatus.  The  postero-superior  margin 
of  the  bone  is  rough  and  cancellous  for  attachment  of  the 
scapular  cartilage  of  elongation.  This  is  a  thin  piece  of 
fibro-cartilage,  extending  upwards  for  about  three  inches, 
having  a  tendency  to  ossification  at  its  attached  margin. 
It  becomes  very  thin  superiorly,  and  curls  inwards.  Ante- 
riorly its  margin  has  a  backward  inclination,  posteriorly  it 
is  continued  as  a  thin  piece  of  cartilage  beyond  the  pos- 
terior angle  of  the  bone.  Its  external  surf  ace  affords  attach- 
ment, anteriorly  to  antea  spinatus,  centrally  to  postea 
spinatus,  and  posteriorly  to  serratus  magnus.  To  its  inner 
surface  the  rhomboidei  are  attached.  The  postero-supeiior 
margin  anteriorly  forms  an  obtuse  angle  with  the  anterior 
margin.  Posteriorly,  in  a  corresponding  manner,  it  joins 
the  postero -inferior  margin,  at  the  extreme  superior  part 
of  which  is  a  triangular  surface  roughened  for  attachment 
of  serratus  magnus.  From  this  the  posterior  margin  of  the 
bone  makes  a  curve  in  a  downward  direction  to  the  inferior 
angle.  Superiorly  this  curve  presents  a  sharp  edge,  to 
which  teres  externus  and  internus,  caput  magnum  of  the 
triceps  extensor  brachii  and  scapulo-ulnaris  are  attached. 
Inferiorly  it  is  more  rounded,  but  still,  for  the  most  part, 
roughened ;  centrally  for  attachment  of  caput  magnum, 
around  which  the  attachment  of  scapulo-humeralis  extends 
in  a  peculiar  manner,  at  the  extreme  inferior  part  of 
scapulo-humeralis  posticus,  externally  of  scapulo-humeralis 
externus,  internally  of  subscapularis.  About  four  inches 
from  its  inferior  part,  in  some  cases,  we  find  a  groove 


OSTEOLOGY.  63 

running  on  to  tlie  external  surface  of  the  bone,  marking 
the  course  of  branclies  of  the  iDOsterior  scapular  vessels. 
The  portion  of  the  bone  opposite  this  is  more  rounded  than 
the  rest,  and  is  termed  the  neck.  Below  it  are  the  cora- 
coid  process  anteriorly,  the  articulatory  surface  for  the 
humerus  posteriorly.  This  articulatory  surface  occupies 
the  inferior  angle.  It  is  termed  the  glenoid  cavity,  and 
is  much  smaller  than  the  head  of  the  humerus  on  which 
it  fits,  thus  allowing  great  range  of  action  of  the  joint.  It 
looks  slightly  downwards  and  backwards,  is  shallow,  and 
presents  a  sharp  margin,  but  at  its  antero-external  part 
manifests  a  slight  tendency  to  extend  on  to  the  external 
surface  of  the  bone.  At  its  anterior  part  it  is  divided  mto 
two  by  a  groove  into  which,  Avhen  the  limb  is  extremely 
bent,  coraco-humeralis  tendon  may  fit.  Externally  to  this 
is  a  roughened  prominence,  near  the  articulatory  surface. 
The  rest  of  the  space  between  the  coracoid  process  and 
the  glenoid  cavity  is  smooth,  and  presents  a  large  foramen 
for  a  blood-vessel  to  pass  into  the  bone.  The  sharp  outer 
circumferent  margin  of  the  glenoid  cavity  affords  attach- 
ment to  the  capsular  ligament  of  the  shoulder- joint. 

The  external  surface  of  the  scapula  is  termed  the 
dorsum.  It  is  convex  in  all  directions,  but  ia  hollowed  out 
in  some  parts  in  such  a  manner  as  to  produce  a  very  pro- 
minent ridge,  extending  from  the  superior  margin  to  the 
neck,  separating  the  anterior  third  from  the  posterior  two 
thirds  of  this  surface.  This  is  the  spine,  and  separates 
this  surface  into  fossa  antea  sjnnatus  anteriorly  and  fossa 
])ostea  sinnatus  posteriorly.  At  its  attached  margin,  and 
superiorly  and  inferiorly,  this  spine  gradually  blends  with 
the  surface  of  the  bone.  Its  free  margin  presents  infe- 
riorly a  roughened  prominence  (corresponding  to  the  acro- 
mion i^rocess  in  man  with  which  the  clavicle  articulates). 
More  superiorly  the  ridge  presents  a  roughness  which 
culminates  in  an  elongated  prominence  with  a  backward 
curve,  the  tubercle,  to  which  the  inferior  anglo^  of  tra- 
pezius is  attached.  The  spine  anteriorly  affords  attachment 
to  antea  spinatus,  posteriorly  to  postea  spinatus  ;  also 
levator  humeri,  teres  externus,  and  (indirectly)  pectoralis 
anticus  gain  attachment  to  its  edge.  Fossa  antea  spinatus 
is  bounded  anteriorly  by  the  anterior  margin,  posteriorly, 
for  the  most  part,  by  the  spine,  superiorly  by  the  postero- 
superior  margin,  inferiorly  it  becomes  widened  in  forming 


64  OUTLINES    OP    EQUINE   ANATOMY. 

the  anterior  part  of  tlie  neck ;  to  its  wliole  extent  is 
attaclied  autea  spinatus.  This  surface  is  increased  by  the 
addition  of  the  space,  bounded  anteriorly  by  the  coraco- 
scapular  ligament,  under  which  the  dorsalis  scapulae  vessels 
and  nerve  wind  round  the  neck  of  the  bone  in  passing  to 
or  from  this  fossa.  Fossa  postea  spinatus  occupies  two 
thirds  of  the  dorsum.  It  is  bounded  posteriorly  by  the 
postero-inferior  margin,  superiorly  by  the  postero- superior 
margin,  anteriorly  by  the  spine.  Superiorly  it  is  smooth, 
affording  attachment  to  postea  spinatus  muscle,  while  the 
inferior  part,  forming  the  posterior  part  of  the  neck,  pre- 
sents roughened  lines  extending  obliquely  upwards  and 
backwards  from  the  inferior  extremity  of  the  spine.  This 
part  gives  attachment  to  scapulo-humeralis  externus,  and 
presents  grooves  running  from  the  posterior  margin  of  the 
bone  to  the  inferior  extremity  of  the  spine,  in  which  a 
branch  of  the  j^osterior  scapular  artery  runs,  sending  off 
the  medullary  artery  of  the  hone  through  a  foramen  in  this 
region.  The  inner  surface  of  the  scapula  is  termed  the 
venter.  It  is  concave  from  before  backwards,  the  concavity 
being  most  marked  along  the  central  line  opposite  the 
spine.  It  is  widest  centrally,  and  superiorly  terminates  in 
a  point  on  reaching  the  cartilage  of  elongation.  Inferiorly 
it  becomes  flat  in  forming  the  neck,  and  again  concave  at 
the  inner  surface  of  the  coracoid  process.  Across  the  neck 
of  the  bone,  from  behind  forwards,  run  branching  grooves 
for  arteries ;  in  other  respects  this  concavity  is  smooth, 
and  it  is  continuous  at  its  .upper  part,  anteriorly  and 
posteriorly  with  two  other  smooth  surfaces,  the  anterior 
of  which  is  smallest  and  bounded  by  a  roughened  line 
running  downwards  and  backwards  from  the  anterior  edge 
of  the  bone ;  the  posterior  is  bounded  by  a  curved  and 
much  rougher  line  extending  from  the  posterior  margin  of 
the  bone  up  against  the  posterior  angle.  This  smooth 
surface,  therefore,  presents  superiorly  three  points  ;  infe- 
riorly it  terminates  at  the  margin  of  the  glenoid  cavity, 
the  inner  surface  of  the  coracoid  process,  and  posteriorly 
the  roughened  line  which  affords  attachment  to  scapulo- 
humeralis  externus.  It  affords  attachment  to  subscapularis, 
between  which,  therefore,  superiorly  are  two  roughened 
triangular  surfaces,  to  which  are  attached  the  anterior  and 
posterior  parts  of  serratus  magnus.  Along  the  inner 
edge  of  the  postero  -  superior  roughened  margin,  and  to 


OSTEOLOGY. 


65 


tlie  inner  surface  of  tlie  cartilage  of  elongation,  are  attached 
the  rliomboidei  muscles. 

HUMERUS  is  a  long  round  bone,  wliicli   is   situated 
below  the  scapula,  running  obliquely  from  above  down- 
wards and  backwards,  forming  with  the  scapula  an  obtuse 
angle  posteriorly.     It  is  a  very  stout  bone,  and  its  superior 
extremity  is  much  larger  than  its  inferior.     The  superior 
extremity  presents  a  head  and  four  tubercles.     The  latter 
form  a  continuous  chain  occupying  the  anterior  part  of 
this  extremity.     The  head  is  situated  at  the  posterior  part 
and  is  convex.     Since  it  looks   directly  upwards  in   the 
natural  position  of  the  bone  it  seems  to  be  inclined  to  the 
posterior    part.     It   extends    slightly    on   to   the    fourth 
tubercle,  and  between  it  and  the  other  tubercles  is  a  space 
elongated  from  side  to  side  with  numerous  large  foramina ; 
this  is  occupied  by  fat  in  the  fresh  subject.     On  the  inner 
side  of  the  upper  extremity  is  a  roughened  process,  broad 
posteriorly,  terminating  in  a  point  anteriorly  in  joining  the 
internal  tubercle  ;  to  this  subscapularis  is  attached.     The 
three  tubercles  on  the  anterior  part  are  termed  respectively 
external,  middle,  and  internal.     The  internal  tuhercle  is  the 
smallest,  receiving  the  termination  of  the  roughened  spot 
just  mentioned,  posteriorly,  and  externally  presents  the 
commencement  of  a   synovial  surface  coated  with  fibro- 
cartilage  which  dips  down  into  the  shallow  fossa  between 
the  internal  and  middle  tubercles  and  then,  after  com- 
pletely covering  the  middle  tuhercle,  dips  into  the  deep  fossa 
between  this  and  the  external  tubercle,  terminating  after 
investing  the  inner  surface  of  the  latter.     Over  this  sur- 
face the  tendon  of  flexor  brachii  plays  ;  hence  it  is  lubricated 
with  synovia,  and  presents  a  large  and  important  bursa, 
which  is  separated   from    the  capsular  ligament  of   the 
joint  by  the  fat  in  the  perforated  space  in  front  of  the 
head.     Below  this  surface  may  be  seen  a  series  of  small 
articular    foramina.     Both     the    external    and    internal 
tubercles  afford  attachment  to  antea  spinatus  and  pectomlis 
magnus  which  serve  to  bind  flexor  brachii  in  its  situation, 
but  the  external  tubercle  gives  the  most  extensive  attach- 
ment and  is  continued  inferiorly  as  a  stout  ridge  much 
roughened,   especially  above   and  below,    superiorly   for 
attachment  of  one  tendon  of  postea  spinatus,  inferiorly  it 
presents  a  tubercular  termination  roughened  and  curved 
slightly  backwards  where  teres  externus  is  attached.  Just 

5 


66  OUTLINES    OF    EQUIXE   ANATOMY. 

beliiud  tlie  ridge  is  a  tria,ugular  roiigliened  space  extending 
to  tlie  fonrtli  tubercle.    To  the  anterior  part  of  this  the  in- 
ferior extremity  of  scapnlo-humeralis  externus  is  attached, 
while  its  inferior  margin  marks  out  the  limit  of  humeralis 
externus  and  the  line  of  attachment  of  caput  medium  of 
triceps  extensor  brachii.     The  foiirth  tuhercle,  situated  ex- 
ternally to  the  head,  is  continuous  with  the  antero- external 
tubercle.     It  has  the  articulatory  surface  for  the  scapula 
extending  on  to  its  internal  surface,  while  its  external  sur- 
face affords  attachment  to  one  head  of  postea  spinatus,  over, 
which  the  other  head  plays,  with  a  bursa  intervening,  to 
become  inserted  into  the  upper  part  of  the  ridge.     Just 
below  the  fourth  tubercle  is  a  row  of  articulatory  foramina. 
The  shaft  of  this  bone  presents  four  surfaces  ;  the  internal 
is  straight ;  superiorly,  just  below  the  roughened  surface 
for  attachment  of  subscapularis,  the  upper  head  of  coraco- 
humeralis  becomes  attached.     Centrally,  at  the  superior 
part  of  the  middle  third,  elongated  from  above  downwards, 
is  a  roughened  ovoid  space  for  insertion  of  the  common 
tendon  of  teres  internus  and  latissimus  dorsi.     Below  this, 
inclined  to  the  anterior  surface,  is  the  attachment  of  the 
lower  head  of  coraco-humeralis ;  between  the  two  heads 
runs  a  branch  of  the  humeral  artery  with  its  satellite  vein 
and  nerve  to  flexor  brachii,  from  behind  forwards,  but  the 
attachment  of  teres  internus  is  a  little  posteriorly  placed 
to  their  connecting  line.     Straight  down  the  limb,  but  in 
consequence  of  the  position  of  the  bone,  oblicjuely  over  its 
inner  surface,  the  humeral  artery  runs  from  the  inner  sur- 
face of  the  shoulder-joint  downwards  to  the  inner  part  of 
the  elbow-joint.    At  the  superior  part  of  the  inferior  third 
of  the  bone  it  gives  off  the  medullary  artery,  which  pierces 
the  medullary  foramen  here  situated.     The  goiTesponding 
vein  is  more  posteriorly  placed.     The  anterior  surface  is 
superiorly  smooth,  mainly  occupied  by  flexor  brachii  run- 
ning downwards,  slightly  inclined  inwards,  after  passing 
over  the  tubercles  of  the  humerus.     The  roughened  attach- 
ment  of   the  long  head  of   coraco-humeralis   encroaches 
upon  this  surface  at  the  superior  part  of  the  inferior  third, 
and  is  separated  by  a  prominent  line  running  downwards 
from  the  ridge  on  the  external  surface,  from  a  deep  de- 
pression just  above  the  lower  articulatory  surface  which 
almost  (in  some  species  of  animals  quite)  extends  through 
the  bone  as  far  as  the  supra- condyloid  fossa.     This  is  the 


OSTEOLOGY.  67 

anterior  fossa  of  the  humerus.  It  presents  many  foramina, 
and  affords  attachment  to  levator  hnmeri  and  pectoralis 
tra-nsversus.  Externally  placed  to  this  the  surface  at  the 
inferior  part  is  very  rough,  bounded  ^posteriorly  by  a  ridge 
which  runs  upwards  and  backwards  from  the  outer  condyle. 
This  ridge  is  most  prominent  inferiorly,  and  there  affords 
attachment  to  extensor  pedis  at  its  lowest  part,  while 
superiorly,  and  to  the  roughened  surface  in  front  of  it,  is 
attached  extensor  metacarpi  magnus  ;  from  the  inferior 
part  to  the  inferior  prominent  extremity  of  the  humeral 
ridge  runs  a  hand  of  mixed  luhite  and  elastic  fibres  which 
gives  attachment  to  panniculus  carnosus,  levator  humeri, 
and  pectoralis  transversus,  and  seems  to  bind  down  hume- 
ralis  externus  in  the  twisted,  wide,  smooth  groove  which 
we  may  trace  from  this  around  the  external  surface  of  the 
bone  bounded  superiorly  by  the  head  and  the  line  running 
from  this  to  the  ridge,  inferiorly  by  a  much  less  prominent 
roughened  line  winding  round  from  the  attachment  of 
subscapularis  at  the  inner  surface  of  the  superior  extremity 
as  far  down  as  the  external  part  of  the  outer  condyle. 
The  lower  part  of  the  posterior  surface  presents  two  ridges 
running  upwards  from  the  condyles  of  which  the  inner  is 
largest  at  its  inferior  extremity  and  runs  straight  upwards, 
while  the  outer,  at  first  insignificant,  proceeds  obliquely 
inwards  and  upwards,  becoming  imperceptibly  blended 
with  the  middle  third  of  the  bone.  It  was  the  external 
margin  of  this  ridge  we  saw  on  the  outer  side  of  the  bone. 
Between  the  ridges  is  the  supra-condyloid  fossa,  deepest  in- 
feriorly, which  serves  to  accommodate  the  hamular  process 
of  the  ulna,  and  in  the  fresh  subject  contains  some  fat. 
Inferiorly  it  presents  an  articulatory  surface  concave  from 
side  to  side  continuous  with  that  of  the  condyles.  To 
the  upper  part  of  the  outer  ridge  anconeus  is  attached, 
while  caput  parvum  arises  from  the  extreme  superior  part 
of  the  inner  ridge.  From  the  inferior  extremity  of  the 
outer,  flexor  metacarpi  externus  arises,  while  the  internal 
ridge  inferiorly  gives  attachment  to  the  common  originat- 
ing tendon  of  perforans  and  perforatus,  and  externally  is 
rough  for  attachment  of  one  head  of  flexor  metacarpi 
medius  and  flexor  metacarpi  internus.  The  rest  of  the 
inferior  extremity  of  the  bone  is  occupied  by  the  articula- 
tory surface  of  the  elbow-joint.  It  consists  of  two  parts 
or  condyles.     The  inner  condyle  is  much  larger  than  the 


68  OUTLINES    OF   EQUINE    ANATOMY. 

outer,  andpreseuts  one  prominent  convex  surface,  decreas- 
ing in  size  towards  the  outer  condyle  whicli  consists  of  two 
convexities.  These  condyles  are  connected  together  by  a 
slight  articulatory  concavity,  which  extends  posteriorly  into 
the  supra- condyloid  fossa.  On  either  side  of  this  extremity 
is  a  depression  for  attachment  of  a  lateral  ligament  of  the 
elbow-joint.  In  the  centre  of  the  articulatory  surface  is  a 
peculiar  roughened  depression  with  rounded  edges  ;  this 
must  not  be  mistaken  for  ulceration. 

RADIUS  AND  ULNA. 

The  basement  structure  of  the  forearm  comprises  two 
bones,  both  of  which,  in  the  ox  and  other  animals,  extend 
to  the  knee.  In  the  horse,  however,  the  posterior  bone  or 
ulna  terminates  about  opposite  the  superior  part  of  the 
inferior  third  of  the  radius  or  anterior  bone,  though  traces 
of  it  may  sometimes  be  seen  united  to  the  inferior  extremity 
at  the  postero-extemal  part.  The  RADIUS  is  a  long  round 
bone,  extending  from  the  elbow  to  the  knee,  presenting  a 
shaft,  a  superior  and  an  inferior  extremity.  The  shaft 
centrally  is  convex  from  side  to  side,  and  oJso  from  above 
downwards.  It  is  smooth  anteriorly,  and  over  it  play 
extensor  metacarpi  and  extensor  pedis.  From  the  outer 
margin  of  the  middle  third  extensor  metacarpi  obliquus 
runs  obliquely  over  this  surface  downwards  and  inwards. 
The  jJosterior  surface  is  slightly  concave  from  side  to  side, 
and  to  its  outer  margin  the  inferior  part  of  the  ulna  is 
attached  to  an  extremely  elongated  triangular  roughened 
surface.  The  rest  of  the  central  part  of  this  surface  affords 
attachment  to  radialis  accessorius  and  the  superior  sus- 
pensory ligament.  The  external  and  internal  sharp  margins 
-afford  attachment  to  the  faschia  which  sustains  the  muscles 
of  the  forearm,  while  more  externally  placed  than  the  ulna, 
extensor  suffraginis  is  situated,  enclosed  between  two 
layers  of  faschia,  one  of  which  is  attached  in  front,  the 
other  behmd  it.  The  ?/jjper  extremity  of  the  radius,  at  the 
-extreme  superior  part,  presents  an  articulatory  surface 
corresponding  to  that  of  the  inferior  extremity  of  the 
humerus.  It  consists  of  an  inner  and  an  outer  part,  almost 
separated  by  a  roughened  groove,  extending  forward  from 
the  posterior  margin  of  the  bone  to  within  about  one  quarter 
qI  an  inch  of  the  anterior  margin,  which  is  here  slightly  in- 


OSTEOLOGY.  69 

dented  backwards.  The  in7ier  surface  for  tlie  large  internal 
condyle  is  concave  in  all  directions,  larger  than  the  outer 
surface,  and  posteriorly  continuous  with  a  synovial  facet 
on  the  posterior  surface  of  the  bone,  which  is  in  apposition 
with  the  inner  synovial  facet  of  the  ulna.  The  outer  surface- 
is  divided  into  two  parts ;  the  inner  part  is  largest  in  every 
way,  and  is  continuous  inwards  at  the  anterior  part  with 
the  outer  half  of  the  articular  surface  ;  outwardly  it  is  con- 
tinuous with  the  outer  small  division.  The  posterior  margin 
of  this  surface  is  continuous  with  the  outer  facet,  which  is 
on  the  posterior  surface,  and  articulates  with  the  ulna.  The 
outer  circumf erent  margin  of  the  whole  articulatoiy  surface 
is  prominent  for  attachment  of  the  capsular  ligament  of 
the  elbow-joint,  and  both  internally  and  externally  below 
it  is  a  roughened  surface  (of  which  the  outer  is  largest)  for 
attachment  of  the  lateral  ligaments  ;  from  the  outer  runs 
extensor  suffraginis,  while  the  inner  is  separated  by  a 
smooth  portion  of  bone  with  slight  transverse  grooves, 
from  a  roughness  on  the  shaft,  to  which  also  the  inner 
lateral  ligament  is  attached,  while  the  tendon  of  humeralis 
externus  runs  under  this  prolongation  of  the  ligament  over 
the  smooth  surface  to  become  attached  to  a  roughened 
space  on  the  posterior  surface,  which  extends  as  far  as  the 
inner  margin  of  the  union  with  the  ulna.  The  anterior 
surface  of  this  extremity  presents  a  prominent  roughened 
tubercle  continuous  with  the  roughened  space  on  the  inner 
part  for  attachment  of  flexor  brachii.  Externally  to  this  is 
a  smooth  surface  with  a  few  foramina.  On  the  posterior 
part  of  the  bone,  inclined  to  the  outer  side  below  the  syno- 
vial  facets  for  the  ulna,  is  a  roughened  space,  to  which 
the  fibrous  band  between  the  bones  is  attached  spreading 
beyond  the  line  of  the  ulna,  on  either  side,  in  its  attachment 
to  the  radius.  Below  this  is  the  radio-ulnar  arch  formed 
by  the  approximation  of  smooth  parts  of  the  two  bones, 
through  which  a  branch  of  the  radial  artery  (vein  and 
nerve)  passes  to  flexor  metacarpi  externus  from  within  out- 
wards. This  space  presents  below  the  medullary  foramen  of 
the  radius,  for  the  artery  during  its  passage  gives  off  the 
nutritive  vessel  of  that  bone.  Below  this  the  union  of  the 
bones  is  ossific,  except  in  the  young  animal,  in  which  it  is 
fibrous.  The  inferior  extremity  of  the  radius  articulates 
with  the  upper  row  of  bones  of  the  knee,  and  for  this 
purpose  presents  three  continuous  articular  facets.     The 


70  OUTLINES    OF    EQUINE    ANATOMY. 

inner  is  the  largest  in  every  respect.  Viewed  from  behind 
forwards  it  is  posteriorly  convex,  anteriorly  concave.  It 
posteriorly  slightly  extends  on  to  the  back  of  the  bone. 
It  articulates  with  os  scaphoides.  Its  anterior,  posterior, 
and  inner  margins  aiford  attachment  to  the  radio-carpal 
capsular  ligament.  Its  outer  abruptly  bends  upwards 
posteriorly  in  commencing  the  articulatory  surface  for  os 
hmare  or  middle  sujface,  which,  after  running  upwards  for 
a  short  distance  at  the  posterior  pp.rt,  bends  outwards,  thus 
producing  a  convexity  posteriorly,  a  concavity  anteriorly, 
separated  from  the  anterior  concavity  of  the  scaphoid  sur- 
face by  a  slightly  prominent  articular  ridge.  It  decreases 
in  size  from  its  inner  to  its  older  margin,  and  is  there  con- 
tinuous with  the  small  convex  articulatory  surface  which 
extends  on  to  the  posterior  surface  of  the  bone,  awd  comes 
anteriorly  in  contact  with  the  cuneiform  bone  posteriorly 
with  trapezium.  The  posterior  surface  of  the  bone  above 
this  articulatory  portion  presents  a  roughened  prominence, 
separated  from  the  middle  articulatory  facet  by  a  deep 
fossa.  This  affords  attachment  to  the  thick  posterior 
annular  ligament  of  the  knee.  Each  side  presents  a  pro- 
minence, the  inner  is  the  largest,  for  attachment  of  a 
lateral  ligament  of  the  knee.  The  outer  prominence  is 
divided  into  two  parts  by  a  groove  running  from  above 
downwards,  through  which  extensor  suffraginis  plays, 
bound  down  by  the  annular  ligament.  The  anterior  sur- 
face inferiorly  presents  four  prominences  for  attachment 
of  the  annular  ligament,  and  three  intervening  grooves.  The 
outer  groove  gives  passage  to  extensor  pedis  tendon,  the 
central  to  extensor  metacarpi  magnus,  the  internal  runs 
obliquely  inwards  and  downwards  as  far  as  the  articular 
surface,  and  gives  passage  to  extensor  metacarpi  obliquus. 
The  ULTTA  is  attached  (as  above  described)  to  the  pos- 
tero-external  ])art  of  the  radius,  superiorly  by  two  small 
synovial  articulatory  facets  connected  with  the  synovial  sur- 
face of  the  elbow- joint.  Below  this  by  a  fibrous  articulation, 
and  at  the  lowest  part  by  an  ossific  union,  and  between  the 
ossific  and  the  fibrous  portion  is  the  radio-ulnar  arch.  The 
ulna  is  divided  into  a  free  and  an  attached  portion.  The 
attached  portion  is  prismatic,  largest  superiorly,  and  from 
this  tapers  downwards,  terminating  insensibly,  blending 
with  the  outer  edge  of  the  posterior  surface  of  the  radius  at 
the  superior  part  of  the  inferior  third.     The  outer  surface 


OSTEOLOGY.  71 

affords  attacliment  to  extensor  suffragiuis,  and  slightly 
to  extensor  pedis.  The  inner  at  the  radio-ulnar  arch  to 
humeralis  externns.  Its  anterior  surface  is  that  attached 
to  the  radius,  while  its  external  and  internal  surfaces  meet 
in  forming  a  rounded  border  posteriorly.  The  free  portion 
or  olecranon  presents  two  surfaces,  three  borders.  The 
anterior  border  is  articulatory,  concave  from  above  down- 
wards, convex  from  within  outwards.  It  extends  most  on 
to  the  onter  surface.  Inferiorly  it  widens,  terminating 
externally  and  internally  in  the  synovial  surfaces  of  the 
attached  portion  of  the  bone.  Frecjuently  only  the  superior 
part  of  this  border  is  smooth,  roughness  extending  com- 
pletely across  it  at  the  inferior  part.  This  surface  articu- 
lates with  the  supra-condyloid  portion  of  the  articulatory 
surface  of  the  humerus,  thus  assisting  to  form  the  elbow- 
joint.  Superiorly  it  forms  an  acute  angle  with  the  antero- 
■superior  margin  which  is  sharp,  and  extends  obliquely 
upwards  and  backwards.  This  angle  is  termed  the  hook- 
like or  hamular  process.  The  antero- superior  margin 
posteriorly  widens  in  joining  the  tuberous  superior  margin, 
which  anteriorly  presents  a  smooth  surface  where  rests  a 
bursa,  and  the  tendon  of  triceps  extensor  brachii  playing 
over  this  becomes  attached  to  the  roughened  part.  The 
external  surface  is  convex,  and  roughened  along  its  central 
line  from  above  downwards  for  attachment  of  some  of 
the  muscular  fibres  of  caput  medium,  and  more  anteriorly 
of  anconeus.  Inferiorly  it  is  smooth  on  becoming  con- 
tinous  with  the  external  surface  of  the  attached  portion  of 
the  bone.  The  inner  surface  is  smooth  and  concave.  At 
its  junction  with  the  superior  margin  it  affords  attachment 
to  one  head  of  flexor  metacarpi  medius  and  to  scapulo- 
nlnaris.  It  blends  with  the  external  surface  in  forming  the 
rounded  j^osterior  margin,  which  is  continuous  with  the 
corresponding  part  of  the  attached  portion,  and  which,  at 
its  junction  with  the  superior  margin,  affords  attachment 
to  ulnaris  accessorius. 


The  CAHPITS—^' wrist"  of  human  subject,  ''knee"  of 
horse— 

■consists  of  seven  or  eight  small  bones  arranged  in  two  rows 
between  the  radius  and  metacarpus.    The  bones  composing 


72  OUTLINES   OF   EQUINE   ANATOMY. 

the  two  i*ows  are  connected  together  by  inter-osseous  liga- 
ments, and  by  other  connecting  ligaments.  The  upper  row 
is  formed  of  four  bones,  which  form  the  radio-carpal  articu- 
lation with  the  radius  ;  between  this  and  the  lower  row, 
which  is  composed  of  three,  sometimes  four,  bones  is  the 
carpal  ginglymoid  or  hinge-like  joint,  while  the  lower  row 
forms  with  the  metacarpus  an  arthrodial  or  gliding  joint, 
carpo-metacarpal.  The  four  hones  of  the  ujp^er  row  are 
the  scaphoid,  lunar,  cuneiform,  and  trapezium  ;  those  of  the 
lower  ro2v,  trapezoides,  magnum,  and  unciforme,  and 
sometimes  the  pisiform  bone. 

OS  SCAPHOIDES  is  irregularly  cubical,  presenting, 
six  surfaces.  It  is  the  inner  bone  of  the  upper  row  and 
articulates  with  radius,  lunare,  trapezoides,  and  magnum. 
Both  its  inferior  and  superior  surfaces  are  articulatory, 
presenting  anteriorly  a  convexity,  continued  anteriorly 
on  to  the  outer  surface,  posteriorly  a  concavity.  But  the 
concavity  is  most  marked  on  the  inferior  surface,  and. 
while  that  of  the  superior  surface  is  continued  for  a  short 
distance  on  to  the  posterior  surface  of  the  bone,  that  of 
the  inferior  surface  does  not  completely  cover  that  surface, 
which  posteriorly  presents  a  roughened  part,  projecting, 
inwards.  The  tq)i)er  surface  articulates  with  the  inner 
prominent  portion  of  the  radius.  The  inferior  surface 
anteriorly  (the  convex  part)  with  os  magnum,  posteriorly 
(the  concave  part)  with  os  trapezoides.  The  space  between, 
the  reflections  of  these  synovial  surfaces  which  articulate 
with  OS  lunare  into  the  outer  surface  of  the  bone  is  flat  but 
rough  for  attachment  of  inter-osseous  ligaments,  as  also  is 
a  concavity  behind  it,  separated  into  a  deep  superior  part, 
and  an  inferior  part  by  a  sharp  ridge.  Posteriorly  the  con- 
cavity is  bounded  by  a  roughened  ridge,  a  continuation  of 
the  posterior  roughened  surface  of  the  bone,  which  is  tuberous, 
below  and  superiorly  presents  a  continuation  of  the  superior 
articular  surface.  This  surface  is  continuous  inwardly 
with  the  interior  and  anterior  surfaces,  both  of  which  are. 
roughened  for  attachment  of  connecting  ligaments  supe- 
riorly and  inf eriorly,  and  of  the  annular  ligament  centrally. 

OS  LUNARE  is  the  centre  bone  of  the  upper  row.  It.  is 
elongated  from  before  backwards,  and  widest  superiorly^ 
It  articulates  with  the  radius,  scaphoides,  cuneiformCj^ 
magnum,  and  unciforme.  It  presents  six  surfaces.  The^ 
superior  surface  is  articulatory,  convex  anteriorly,  concave- 


OSTEOLOGY.  /o 

posteriorly,  terminating  behind  in  a  point  wliicli  extends 
upwards.  Its  outer  margin  also  anteriorly  terminates  in  a 
point.  This  surface  articulates  with  the  central  part  of  the 
inferior  articulatorj  surface  of  the  radius,  the  vertical  por- 
tion of  which  corresponds  to  a  continuation  of  this  smooth 
articulatory  surface  on  to  the  inner  surface  of  os  lunare, 
which  surface,  at  its  antero- superior  part,  also  comes  in  ap- 
position with  OS  scaphoides.  This  surface,  too,  is  continued 
on  to  the  external  part  of  the  bone  anteriorly,  where  it  plays 
on  OS  cuneif orme.  The  inferior  surface  presents  two  parts, 
inner  of  which  is  convex  anteriorly,  concave  posteriorly, 
extending  from  the  anterior  to  the  posterior  margin  of  the 
bone.  It  articulates  with  os  magnum,  and  anteriorly  is. 
continued  on  to  the  internal  surface,  forming  a  small 
articulatory  facet  for  os  scaphoides.  The  outer  portion  of 
the  inferior  surface  is  convex,  anteriorly  placed  and  comes 
into  connection  with  os  unciforme.  It  is  continuous  with 
the  lower  facet  on  the  outer  surface,  on  which  os  cunei- 
forme  plays.  The  anterior  surface  is  slightly  roughened^ 
for  attachment  of  connecting  and  the  annular  ligaments 
The  imsterior  surface  superiorly  is  concave,  inferiorly  pro- 
minent ;  it  also  gives  attachment  to  the  annular  ligament. 
The  outer  surface  presents  posteriorly,  the  outer  surface  of 
this  roughened  prominence  antero-superiorly,  and  antero- 
inf  eriorly  are  the  articulatory  facets  for  os  cuneif  orme.  The 
space  between  them  is  concave  and  rough  for  attachment 
of  interosseous  ligaments.  The  inner  surface  superiorly  along 
its  whole  length  presents  the  vertical  articulation  for  the 
radius,  which  anteriorly  is  continuous  with  a  small  surface 
for  OS  scaphoides,  which  is  also  in  contact  with  a  corre- 
sponding facet  at  the  antero -mferior  part  continued  from 
the  inferior  surface.  The  space  between  these  is  rough  for 
attachment  of  interosseous  ligaments. 

OS  CTJNEIFORME  is  situated  at  the  outer  part  of  the 
upper  row.  It  articulates  with  radius,  lunare,  unciforme, 
and  trapezium.  It  presents  two  surfaces  and  four  borders^- 
The  external  surface  is  convex  in  every  direction,  and  is- 
roughened  for  attachment  of  the  annular,  connecting,  and 
outer  lateral  ligaments.  Along  its  postero-superior  margin  it 
presents  a  roughened  groove  for  attachment  of  the  capsular 
ligament  of  its  articulation  with  trapezium.  The  internal 
surface  presents  anteriorly  two  smooth  articulatory  facets, 
one  superiorly  continued  as  far  as  the  anterior  margin,  con- 


74  OUTLINES    OF    EQUINE   ANATOMY. 

tinuous  with  the  articulatoiy  surface  on  its  superior  margin  ; 
one  inferioiiy,  separated  by  a  roughened  space  from  the 
anterior  margin,  continuous  with  the  articulatorj  surface 
of  the  inferior  margin.  Between  and  behind  these  this 
surface  is  roughened  for  attachment  of  interosseous  liga- 
ments, posteriorly  it  terminates  in  a  point.  The  superior 
margin  presents  a  smooth  triangular  concave  surface  for 
articulation  with  the  radius  continuous  with  the  superior 
one  on  the  internal  surface  for  lunare.  T]iq  inferior  surface 
or  margin  presents  an  articulatory  surface  with  the  unciform, 
which  anteriorly  is  concave,  posteriorly  at  the  external  side 
convex.  It  is  continuous  with  the  inferior  facet  on  the 
inner  surface  for  lunare.  It  is  separated  by  a  roughened 
space  from  the  ]30sterior  margin,  which  presents  a  concave 
ovoid  articulatory  surface  extending  obliquely  forwards 
and  u^^wards  ;  with  this  the  inferior  articulatory  surface  of 
trapezium  comes  in  contact.  It  is  separated  from  the 
inferior  articulation  by  a  roughened  dexn'ession,  to  which 
its  capsular  ligament  is  attached.  The  anterior  margin  of 
the  bone  is  also  roughened  for  ligamentous  attachment. 

OS  TRAPEZIUM  is  situated  at  the  postero-external  part 
of  the  upper  row.  It  is  flattened  from  side  to  side,  and 
slightly  curved  inwards.  It  presents  two  surfaces  and  four 
margins.  The  anterior  margin  has  two  articulatory  facets, 
the  superior  concave  for  articulation  with  the  radius,  and 
extending  on  to  the  internal  surface  of  the  bone.  It  is  sepa- 
rated by  a  deep  perforated  groove  from  the  inferior  facet, 
which  is  below  and  slightly  externally  placed,  convex  for 
articulation  with  cuueforme  ;  internally  placed  to  this  the 
anterior  margin  is  rough.  The  superior  and  inferior  margins 
are  rough,  and  extend  from  the  anterior  to  the  posterior 
margin.  The  superior  is  sharpest,  and  from  about  its  centre 
over  the  external  surface  of  the  bone  a  roughened  groove 
extends  towards  the  infero- anterior  articulatory  facet. 
Flexores  metacarpi  externus  et  medius  are  attached  to  the 
upper  margin,  and  through  the  groove  on  the  external  sur- 
face a  rounded  tendon  of  flexor  metacarpi  externus  runs  to 
the  outer  small  metacarpal  bone.  This  groove  presents  a 
prominent  roughened  edge,  separating  it  from  a  depression  ; 
the  rest  of  the  external  surface  is  convex  and  roughened  for 
attachment  of  the  annular  ligament,  which  is  also  attached 
to  the  inferior  margin  and  to  the  posterior  margin,  which 
is  rounded  and  rough.     The  internal  surface  is  concave  and 


OSTEOLOGY. 


75 


sligMly  rougli  for  attacliment  of  the  annular  ligament. 
At'^its  antero-superior  part  it  presents  a  small  articulatory 
facet  continuous  with  the  superior  facet  on  the  anterior 
margin.  From  this  a  ridge  runs  downwards  and  backwards 
obliquely  to  the  inferior  margin. 

-  OS  TRAPEZOIDES  is  the  inner  bone  of  the  lower  row, 
and  articulates  with  magnum,  scaphoides,  metacarpi  mag- 
num, and  parvum  internum  (sometimes  with  pisiform). 
It  presents  three  surfaces.  The  supero-iuternal  surf  ace  pre- 
sents superiorly  a  rounded  convexity,  which  commencing 
in  a  point  at  the  outer  margin  anteriorly  occupies  the  whole 
upper  part  of  the  bone,  and  passes  to  the  postero-internal 
part,  extending  about  halfway  down  to  the  lower  surface. 
Around  it  runs  a  narrow  groove,  exce^Dt  at  the  outer  part, 
where  it  is  continuous  with  a  small  elongated  facet,  articu- 
latory for  OS  magnum.  The  rest  of  this  surface  is  roughened 
for  attachment  of  the  annular,  inner  lateral,  and  connecting 
ligaments.  Along  the  inferior  margin  is  a  groove  which 
bounds  the  inferior  articulatory  surface.  The  inferior  surface 
is  mainly  occupied  by  a  flat  facet  for  articulation  with  the 
inner  small  metacarpal  bone,  elongated  from  before  back- 
wards, posteriorly  continuous  with  a  smaller  facet  for  os 
metacarpi  magnum,  and  this  in  turn  is  continuous  with  a 
still  smaller  facet  for  os  magnum.  This  articulatory  sur- 
face is  bounded  on  every  side  by  a  groove,  except  on  the 
outer,  where  it  is  reflected  on  to  the  outer  surface  for  arti- 
culation with  OS  magnum.  Between  the  superior  facet 
(continuous  with  the  upper  surface)  and  the  inferior  facet 
(continuous  with  the  lower  surface)  the  outer  part  of  the 
bone  is  roughened  for  attachment  of  interosseous  ligaments. 
Postero-inferiorly  is  a  peculiar  prominence  presenting  a 
sharp  point  inwards,  bounded  by  the  posterior  surface  for 
OS  magnum  posteriorly,  inferiorly  by  the  facet  for  os  meta- 
carpi magnum. 

OS  MAGNUM  is  the  central  bone  of  the  lower  row,  and 
articulates  with  lunare,  scaphoides,  trapezoides,  unciforme, 
metacarpi  magnum,  et  parvum  internum.  It  has  five 
surfaces,  which  give  it  a  triangular  appearance,  and  is  flat- 
tened from  above  downwards,  having  a  base  or  anterior 
surface,  and  an  apex  or  posterior  angle  which  is  rounded. 
The  superior  surface  is  triangular  and  presents  two  articu- 
latory portions  which  blend  anteriorly.  The  outer  consists 
of  two  triangular  portions  united  at  their  apices,  occu- 


76  OUTLINES    OF    EQUINE    ANATOMY. 

pying  tlie  inner  half  of  tlie  surface,  extending  from  tlie 
anterior  margin  to  the  posterior  angle.  The  posterior 
triangle,  convex  and  rounded,  extends  on  to  the  posterior 
angle  of  the  bone.  The  anterior  triangle  is  continuous  on. 
its  outer  margin  with  a  facet,  on  the  anterior  part  of  the 
outer  surface  for  os  unciforme.  Internally  it  is  con- 
tinuous with  the  inner  articulatory  part  of  this  surface, 
which  is  triangular,  occupying  the  inner  angle  of  the 
surface,  separated  postero-externally  from  the  other  part 
by  a  perforated  concavity.  It  is  slightly  continued  on  to- 
the  inner  surface  of  the  bone  for  articulation  with  trape- 
zoides.  "With  this  part  os  scaphoides  comes  in  contact,  while 
OS  lunare  occupies  the  outer  part.  The  inferior  surface  is 
flattened,  slightly  convex  anteriorly,  slightly  concave  pos- 
teriorly, and  has  four  margins.  The  anterior  margin  is. 
convex,  extending  farthest  backward  on  the  inner  side. 
The  posterior  is  not  half  the  length  of  this,  and  is  perfectly 
straight.  The  outer  margin  is  straight,  but  centrally  pre- 
sents a  deep  depression,  roughened,  and  extending  towards 
the  centre  of  the  surface.  Along  the  inner  margin,  at  its 
anterior  part,  is  a  small  facet  for  articulation  with  the 
inner  small  metacarpal  bone  ;  this  is  continuous  with  the 
main  surface  for  os  metacarpi  magnum,  and  is  continued  on 
to  the  inner  surface,  forming  a  small  facet  for  the  trape- 
zoid. The  inner  surface  presents  three  facets  for  trape- 
zoides — one  antero-superiorly  elongated,  one  antero-infe- 
riorly,  shorter  but  deeper,  and  one  posteriorly  extending^ 
from  the  posterior  part  of  the  inner  concavity  of  the 
inferior  surface  ;  this  looks  forwards.  The  rest  of  the 
surface  presents  irregular  roughened  concavities  and 
convexities  for  attachment  of  interosseous  ligaments. _  The 
outer  surface  presents  articulatory  facets  for  union  with  os- 
unciform,  between  which  the  bone  is  rough  for  attach- 
ment of  interosseous  ligaments.  The  anterior  surface  or 
base  forms  an  irregular  parallelogram  extended  from  side 
to  side,  which  centrally  presents  a  roughened  prominence 
for  attachment  of  the  annular  ligaments,  superiorly  and 
inferiorly  a  groove  bounded  by  the  articular  facets  of  the 
upper  and  lower  surfaces, 

OS  UNCIFORME.— The  outer  bone  of  the  lower  row 
articulates  with  cuneiforme,  lunare,  magnum,  metacarpi 
magnum,  et  parvum  externum.  It  presents  four  surfaces,, 
and  a  posterior  very  prominent  angle.     The  su])ero- external 


OSTEOLOGY.  77 

surface  presents  an  articulately  convexity  extending  obli- 
quely downwards,  outwards,  and  backwards.  The  outer 
part  of  this  articulates  with  cuneiforme,  the  inner  with 
lunare  and  extends  to  a  superior  facet  on  the  inner  surface 
for  articulation  with  magnum.  The  inferior  s?M/ace  presents 
three  articular  parts,  the  anterior,  extending  obliquely 
outwards  and  backwards,  internally  continuous  with  the 
inferior  facet  for  magnum  on  the  internal  surface.  It 
articulates  with  metacarpi  magnum,  as  also  does  the 
posterior  part,  which  slightly  meets  the  former  by  its 
anterior  angle,  but  is  separated  from  it  inwardly  by  an 
indentation  on  its  inner  margin,  externally  by  the  middle 
part  of  the  surface,  which  articulates  with  the  outer  small 
metacarpal  bone.  This  surface  presents  a  semicircular 
figure,  and  a  groove  extends  round  its  outer  margin.  The 
in7ier  surface  so  exactly  corresponds  with  the  outer  surface 
of  OS  magnum  that  one  description  will  suffice  for  both. 
The  posterior  facet  is  on  the  inner  side  of  the  process,  the 
outer,  posterior,  and  superior  parts  of  which  are  rough,  as 
also  is  the  anterior  surface,  affording  attachment  to  the 
annular  ligaments,  bounded  on  every  side  by  grooves 
mapping  out  the  articulatory  facets  of  the  neighbouring 
surfaces. 

OS  PISIFORME  is  a  small  osseous  nodule  found  on  the 
inner  side  of  the  lower  row,  articulating  with  trapezoides, 
and  the  inner  small  metacarpal  bone,  for  which  it  presents 
small  articulatory  facets.  Its  presence  is  by  no  means 
constant ;  it  is  relatively  larger  in  the  ass  than  in  the 
horse. 

THE  METACARPUS 

is  formed  of  three  bones,  the  largest  of  which  is  centrally 
placed,  with  a  smaller  one  on  each  side  of  it.  It  extends 
from  the  knee  to  the  fetlock,  but  the  small  bones  only 
proceed  downwards  part  of  this  distance. 

OS  METACARPI  MAGNUM  (CANON  OR  SHANK 
BONE)  is  a  long,  round  bone,  extending  from  the  knee  to 
the  fetlock,  having  two  extremities  and  a  shaft.  The 
shaft  is  flattened  from  behind  forwards,  and  presents  two 
surfaces  connected  by  Iwo  rounded  margins.  The  anterior 
surface  extends  in  a  straight  line  from  above  downwards, 
is  convex  and  rounded  from  side  to  side,  becoming  flat- 
tened, and  li^.ore  expanded  superiorly  and  inferiorly.     It  is 


78  OUTLINES    OF    EQUINE    ANATOMY. 

for  tlie  most  part  smooth,  and  is  separated  from  tlie  skin 
only  by  tlie  expanded  tendons  of  extensor  pedis  and 
extensor  snffraginis,  wliicli  run  from  above  downwards 
inclined  to  the  outer  side,  and  are  closely  connected  to- 
gether. At  its  extreme  superior  part  it  presents  a  groove 
marking  out  the  limit  of  the  superior  articulatory  surface, 
and  below  this  is  roughened,  especially  on  the  inner  side, 
where  is  a  roughened  prominence  for  attachment  of  ex- 
tensor metacarpi  magnus.  The  j^osterior  surface  is  flattened, 
and  on  either  side  presents  a  roughened  surface  for  attach- 
ment of  the  metacarpal  interosseous  ligaments,  binding  the 
small  to  the  large  bone.  These  surfaces  are  widest  supe- 
riorly and  inferiorly,  taper  to  a  point  slightly  con- 
verging, extendmg  to  about  the  inferior  part  of  the  middle 
third  of  the  bone.  The  space  between  them  is  concave, 
and  at  the  inferior  part  of  the  superior  third  inclined  to 
the  inner  side  presents  the  medullary  foramen,  through 
which  a  branch  of  the  small  metacarpal  artery  runs  to 
supply  the  bone.  The  extreme  superior  part  of  this 
surface  affords  attachment  to  the  superior  extremity  of  the 
superior  sesamoideal  ligament,  the  anterior  surface  of 
which  lies  in  contact  with  the  greater  part  of  the  rest  of 
this  surface,  which,  superiorly  convex,  at  the  lower  part  of 
the  middle  third  becomes  concave  centrally,  agam  be- 
coming 2:>romment,  especially  along  the  middle  line  in 
reaching  the  inferior  articulatory  surface.  Here  it  is 
pierced  by  a  row  of  articular  foramina.  The  margins  of 
the  bone  superiorly  are  roughened  for  attachment  of  the 
capsular  (car po -metacarpal)  and  annular  ligaments  of  the 
knee,  centrally  are  smooth,  forming  with  the  small  meta- 
carpals grooves  running  from  above  downwards.  Infe- 
riorly they  are  rough  for  attachment  of  a  ligament  from 
the  inferior  extremity  of  the  small  metacarpal  bone,  and 
one  from  the  lateral  part  of  the  sesamoid  bone,  and  below 
this  present  each  side  a  rounded  concavity  for  attachment 
of  the  lateral  ligaments  of  the  fetlock.  The  tijpper  surface 
of  the  bone  presents  four  distinct  articulatory  facets.  One 
is  by  far  the  largest  and  slants  obliquely  inwards,  and 
occupies  the  inner  two -thirds  of  the  surface.  It  articu- 
lates with  OS  magnum  and  presents  four  margins.  The 
anterior  margin  has  two  convexities  and  extends  farthest 
backwards  on  the  inner  side,  and  there  meets  the  inner 
margin    which    runs    obliquely    from    within     outwards 


OSTEOLOGY.  79 

and  backwards.  It  is  divided  into  an  anterior  and  a 
posterior  part  by  a  break  in  tlie  margin.  The  anterior 
part  is  continued  on  to  tke  posterior  surface  in  forming  the 
small  anterior  articulatory  facet  for  the  inner  small  meta- 
carpal bone.  The  posterior  part  is  continuous  with  a  small 
facet  for  os  trapezoides  which,  in  its  turn,  joins  an  ex- 
tremely small  one  for  os  metacarpi  parvum  internum.  The 
posterior  margin  is  perfectly  straight  and  about  half  the 
size  of  the  anterior.  The  outer  margin  anteriorly  and 
posteriorly  is  continuous  with  circulatory  facets  sloping 
outwards,  separated  by  a  deep  roughened  dejDression, 
These  articulate  with  os  unciforme,  and  are  each  con- 
tinuous with  an  articulatory  facet  on  the  posterior  surface 
for  the  external  small  metacarpal  bone.  The  iiiferior  arti- 
culatory surface  is  convex  in  every  direction,  and  consists 
of  three  prominences  running  from  behind  forwards.  The 
central  prominence  is  most  marked,  narrowest,  and  extends 
farthest  both  anteriorly  and  posteriorly.  It  is  wholly 
articulatory.  The  inner  and  outer  prominences  consist 
of  surfaces  sloping  towards  the  central  ridge.  They  are 
coated  with  cartilage  continuous  with  that  of  the  central 
ridge.  In  most  cases  the  inner  is  larger  than  the  outer 
articulatory  surfaces. 

OSS  A  METACARPI'  PARVA  are  extremely  elongated 
small  bones,  placed  at  the  lateral,  inclined  to  the  posterior, 
part  of  the  large  metacarpal  bone.  They  decrease  in  size 
from  above  downwards,  terminating  iv/eriorly  oj^posite  the 
inferior  part  of  the  middle  third  of  the  large  bone  in  small 
rounded  bulbs,  from  which  the  superior  ligament  of  the 
pad,  and  a  small  ligament  to  the  infero-lateral  part  of  the 
large  bone,  run  downwards.  The  siq^erior  extremity  is  rough 
and  tuberous  for  the  most  part,  while  superiorly  it  is  more 
or  less  occupied  by  ai'ticulatory  surfaces,  which  extend 
slightly  on  to  the  attached  part  as  two  synovial  facets 
for  OS  metacarpi  magnum.  Below  this  the  whole  attached 
surface  is  roughened  for  the  white  fibrous  connection  with 
the  large  bone.  The  inner  and  otder  surfaces  are  smooth, 
and  from  the  inner  runs  the  anterior  lumbricus  muscle, 
while  the  outer,  with  the  large  bone,  forms  a  smooth 
groove. 

The  inner  small  metacarjKil  hone  at  its  upper  extremity  is 
for  the  most  part  flat  for  articulation  with  os  trapezoides. 
Its  outer  margin  anteriorly  presents   an   almost  vertical 


80  OUTLINES    OF    EQUINE    ANATOMY. 

aTticulatory  facet  to  blend  witli  that  of  tlie  large  bone, 
wbicb  articulates  with  os  magnum,  while  postero-externally 
is  a  small  facet  for  connection  with  os  pisiforme.  It  gives 
attachment  to  extensor  metacarpi  obliquus  and  flexores 
nietacarpi  internus  and  medius,  the  latter  through  the 
medium  of  the  annular  ligament  of  the  knee.  To  it  also 
is  attached  the  inner  lateral  ligament  of  that  joint.  It  is 
larger  and  longer  than  the  outer  small  bone. 

The  outer  small  metacarjxil  hone  supero-externally  is 
rough  for  attachment  of  the  outer  lateral,  and  the  annular 
ligament  of  the  knee,  also  of  flexor  metacarpi  externus. 
Supero-internally  it  presents  an  articulatory  surface,  flat 
and  slanting  inwards,  on  which  os  unciforme  glides. 

SESAMOID  BONES,  two  in  number  in  each  limb,  are 
situated  at  the  fetlock  behind  the  inferior  extremity  of  the 
large  metacarpal  bone  on  which  they  play,  f  .)r  their  anterior 
surfaces  are  articulatory,  and  they  are  so  united  together 
that  the  surfaces  of  the  two  bones  form  the  counterpart 
of  the  posterior  part  of  the  inferior  extremity  of  the  large 
metacarpal  bone.  Each  bone  presents  four  surfaces.  The 
anterior  surface  is  triangular  and  articulatory,  consists  ex- 
ternally of  a  large  smooth  surface,  which  inwardly  becomes 
reflected  backwards  in  forming  with  its  fellow  the  counter- 
part of  the  central  ridge  of  the  inferior  extremity  of  the 
large  metacarpal  bone.  This  surface  inwardly  is  connected 
by  the  inner  margin  to  \\iq  ]josterior  surface.  This  margin 
gives  attachment  to  the  intersesamoid  ligament  which 
binds  the  bones  together,  and  thus  renders  their  posterior 
surfaces  which  are  coated  with  fibro-cartilage,  a  convenient 
groove  for  the  flexor  tendons  to  play  over.  The  inferior 
surface  is  rough,  triangular,  and  presents  foramina  ;  from 
it  the  inferior  sesamoid  ligaments  extend.  The  outer  sur- 
face inclines  obliquely  upwards  and  inwards  in  such  a 
manner  as  to  form  a  point  superiorly  in  meeting  the  anterior 
and  posterior  surfaces.  The  posterior  margin  of  this  sur- 
face presents  a  prominent  ridge,  and  anteriorly  some  large 
foramina.  From  the  ridge  the  lateral  sessamoid  ligaments 
run,  and  also  to  the  ridge  are  attached  those  portions  of 
the  superior  sesamoideal  ligament  which  pass  to  extensor 
pedis,  and  also  the  annular  ligaments  of  the  fetlock. 

OS  SDEFRAGINIS  is  the  long  roimd  bone  which  extends 
from  the  fetlock  to  the  pastern  joint.  Its  shaft  is  short  and 
slightly  compressed  from  before  backwards.     The  anterior 


OSTEOLOGY.  81 

surface  is  convex  from  side  to  side,  and  is  mainly  occupied 
by  tlie  extensor  pedis  tendon  with  the  bands  running  to  it 
from  the  superior- sessamoideal  ligament.  It  is,  therefore, 
smooth  for  the  most  part,  but  above  and  below  it  becomes 
roughened.  Superiorly  it  is  ]3rominent  for  attachment  of 
the  tendon  of  extensor  suffraginis  (or  ligamentum  exten- 
sorum).  This  prominence  is  slightly  inclined  to  the  outer 
side.  The  ijosterior  surface  is  also  convex,  and  superiorly 
presents  externally  and  internally  two  prominent  angles 
from  which  two  ridges  converge  to  form  a  prominent  rough 
surface  at  the  central  part,  to  which  the  short  part  of  the 
inferior  sessamoideal  ligaments  is  attached.  To  the  angles, 
are  attached  white  fibrous  bands,  which  converge  in  be- 
coming attached  to  the  posterior  surface  of  the  perforatus 
tendon  ;  they  are  parts  of  the  annular  ligament  of  the  fet- 
loch.  The  margins  of  this  bone  lie  in  contact  with  the  plantar 
vessels  and  nerves,  and  inferiorly  present  a  roughened  line, 
to  which  the  superior  ligament  of  the  navicular  bone  is  at- 
tached in  blending  with  the  lateral  hgament  of  the  pastern 
joint.  The  superior  articulatory  surface  of  the  bone  is  in 
every  respect  concave,  and  presents  three  concavities,  the 
inner  and  outer  of  which  are  triangular;  the  inner  is  shghtly 
the  largest.  The  central  concavity  is  deepest  and  narrowest, 
extending  from  the  anterior  to  the  posterior  surface,  while 
between  "it  and  the  above-mentioned  ridges  is  a  rougher 
space  perforated  by  numerous  foramina.  The  inferior  ex- 
tremity is  much  smaller  than  the  superior,  and  presents  an 
irregularly  heart-shaped  articulation,  which,  by  uniting 
with  the  upper  extremity  of  os  coronse,  fonus  the  pastern 
joint.  This  is  obtusely  rounded  anteriorly,  extending 
shghtly  on  to  the  anterior  surface,  and  consists  of  two 
roimded  convexities,  which  meet  forming  a  shallow  groove. 
They  extend  considerably  on  to  the  posterior  surface,  and 
are  here  separated  by  a  roughened  indentation ;  the  inner 
is  slightly  the  largest.  On  either  side,  slightly  inclined  to 
the  anterior  part,  just  above  the  articulation,  the  lateral 
ligaments  of  the  pastern  are  attached.  Posteriorly,  above 
the  articulatory  surface,  are  numerous  foramina. 

Ossa  coronse,  pedis,  and  naviciilare  will  be  examined  in 
dissection  of  the  foot. 


82  OUTLINES    OF   EQUINE   ANATOMY. 

BONES  OF  THE  HIND  LIMB. 

The  posterior  cavity  of  tlie  "body  is  termed  ttie  pelvis.  It 
is  most  marked  in  tlie  skeleton  for  in  tlie  fresli  subject  it  is 
anteriorly  confounded  witli  the  posterior  part  of  the  abdo- 
men. Its  basement  structure  consists  of  two  bones  (each 
composed  of  smaller  portions  connected  together  by  liga- 
ments), superiorly  is  the  sacrum  which  has  been  described  as 
part  of  the  spinal  column.  Inferiorly  and  lateral^  are  the 
ossa  innominata. 

OSSA  INNOMINATA  are  two  in  number,  one  on  each 
side,  and  these  are  united  at  the  inferior  part  centrally 
forming  the  symjohysis.  These  bones  originally  consist 
each  of  three  parts,  but  in  the  adult  these  parts  are  firmly 
united  to  form  one  bone.  Supero-anteriorly  is  the  ilium 
forming  the  lateral  boundary  of  the  pelvis  at  the  ante- 
rior part;  antero-inferiorly  is  os  pubis;  postero -inferiorly 
OS  ischium.  The  three  unite  in  forming  a  cotyloid  cavity 
termed  the  acetabulum,  coated  with  articular  cartilage 
with  a  gap  extending  from  its  inner  and  anterior  part 
towards  the  centre,  where  ligamentum  teres  which  serves 
to  maintain  the  cavity  in  contact  with  the  head  of  the 
femur,  is  attached.  It  is  deep  in  all  parts  and  is  rendered 
more  so  by  a  band  of  fibro-cartilage  (circumferential  or 
cotyloid)  which  is  attached  around  its  margin,  and  is  con- 
tinued across  the  gap  forming  the  transverse  ligament, 
and  binding  down  the  pubio-femoral  ligament  in  its 
passage  to  the  head  of  the  femur.  The  ischium  forms 
the  major  portion  of  this  cavity  (about  three-fifths),  while 
the  pubis  forms  the  least,  a  little  less  than  one-fifth,  os 
ilium  forming  a  little  more  than  one-fifth  ;  but  a  consider- 
able j)art  of  the  pubis  is  occupied  by  the  roughened 
groove  extending  inwards.  The  acetabulum  looks  outwards 
and  slightly  downwards  and  backwards. 

OS  ILIUM  is  a  flat  bone,  triangular  in  shape,  placed 
obliquely  from  above  downwards  and  outwards.  It  is  tri- 
angular, and  presents  two  surfaces,  three  margins,  and  three 
angles.  The  antero -inferior  angle  is  termed  the  antero- 
inferior spinous  process,  it  is  rough  and  tuberous,  elongated 
from  above  downwards  presenting  four  prominences,  two 
superiorly,  two  inferiorly.  It  affords  attachment  internally 
to  iliacus,  longissimus  dorsi,  obliquus  abdominis  externus, 
obliquus  abdominis  internus,  transversalis  abdominis,  and 


OSTEOLOGY.  S3 

quadratus   luuiborum.       Externally   gluteus    maximus    is 
attached  to  it,  and  from  its  inferior  tubercles  runs  the 
common  tendon   of  tensor  vaginae  and  gluteus  externus. 
The  siqjerior  angle  is  the  supero-posterior  spinous  process, 
it  is  elongated,  flattened  from  within  outwards,  and  sujdo- 
riorly  is  curled  slightly  outvvards.     To  it  runs  the  superior 
ilio-sacral  ligament,  from  its  posterior  margin  the  inferior 
ilio-sacral    ligament.      To   its  inner  surface   is  attached 
longissimus    dorsi,  and  to    its    external    surface   gluteus 
maximus  ;  while  gluteus  externus,  in  some  cases,  seems  to 
arise  from  its  summit.     The  inferior  angle  becomes  rounded 
in  forming  the  neck,  which  is  convex,  and  below  dilates  to 
form  the  anterior  part  of  the  acetabulum  inferiorly,  the 
union  with  the  neck  of  the  ischium,  externo- superiorly,  the 
junction  with  the  os  pubis  antero-internally.     The  external 
surface  of  the  ilium  is  called  the  dorsum,  and  is  concave, 
looking  upwards,  outwards,  and  backwards.     It  becomes 
convex  in  forming  the   neck.     Superiorly   to   the   upper 
margin  it  affords  attachment  to  gluteus  maximus,  and  this 
muscle  is  firmly  attached  to  it  as  far  as  a  crescentic  groove, 
running  across  its  neck  where  gluteus  internus  commences, 
and  becomes  attached  as  far  down  as  the  acetabulum.  The 
margin  connecting  the  anterior  and  superior  angles  is  slightly 
concave,  and  is  rough  and  thickened.     It  is  termed  the 
crista,  and  affords  firm  attachment  to  the  tendinous  struc- 
ture of  longissimus  dorsi.     The  anterior  7nargin  is  concave, 
and  looks  downwards  and  outwards,  it  is  smooth,  affords 
internally  attachment  to  iliacus,  externally  to  the  glutei 
muscles,   and   inferiorly   at  the   neck    becomes   widened, 
forming  two  roughened  fossae  separated  by  a  smooth  space. 
To  these,  one  of  which  is  inclined  to  the  dorsum,  the  other 
to  the  venter  surface,  are  attached  the  two  heads  of  rectus 
f emoris  ;  between  them  is  a  small  quantity  of  fat.  Below  this 
ilio-femoralis  arises,  above  it  psoas  parvus  is  inserted.  The 
jposterior  margin  is  divided  into  three  parts.     The  superior 
third  gives  attachment  to  the  inferior  ilio-sacral  ligament, 
the  middle  is  smooth  for  passage  of  gluteal  vessels  and 
nerves  round  it  from  within  outwards,  the  inferior  forms 
a  very  sharp  prominent  ridge  continued  on  to  the  neck  of 
the  ischium,  to  which  the  sacro- sciatic  ligament  is  attached. 
This  is  the  ischiatic  spine,  and  externally  is  continuous  with 
a  small  but  very  rough  space  for  attachment  of  part  of 
gluteus   internus.     The   internal  surface  of  the   ilium  is 


84  OUTLINES    OF   EQUINE    ANATOMY. 

termed  the  venter.  It  is  convex  for  tlie  most  part,  and  is 
•divided  into  two  portions  by  a  roughened  articulatory 
surface  for  the  transverse  process  of  the  first  sacral  bone. 
This  articular  surface  {auricular  facet)  looks  obliquely 
downwards  and  forwards,  and  is  smoothest  centrally, 
where  is  sometimes  found  a  small  synovial  cavity.  Its 
outer  margin  is  very  rough  for  attachment  of  the  sacro- 
iliac ligament.  The  surface  anteriorly  placed  to  this,  which 
)liel23S  to  form  the  brim  of  the  pelvis,  is  triangular,  termi- 
jjating  in  a  point  inferiorly.  It  gives  attachment  to  the 
iliacus,  and  that  portion  of  it  which  forms  the  anterior 
l>art  of  the  neck  presents  transverse  grooves,  through 
which  runs  the  arteria  innominata  from  behind  forwards 
in  its  course  to  the  triceps  cruralis.  This  surface  is  sej^a- 
a-ated  from  the  posterior  surface,  which  is  much  narrower, 
and  gives  origin  to  pyriformis,  by  grooves  running  directly 
•downwards  to  the  obturator  foramen,  through  which  the 
obturator  vessels  and  nerve  pass.  In  contact  with  this 
surface  superiorly  and  under  the  first  sacral  transverse  pro- 
cesses are  the  iliac  arteries  andtheir  commencing  branches, 
also  the  external,  internal,  and  common  iliac  veins. 

OS  ISCHIUM  occupies  the  postero -inferior  part  of  the 
pelvis,  and  consists  of  three  processes  with  the  body 
at  which  they  join.  The  antero-exiernal  jjrocess  runs  for- 
wards to  help  to  form  the  acetabulum,  consequently  the 
superior  part  of  its  anterior  surface  is  roughened  for 
articulation  with  the  ilium  and  its  infero-anterior  j^art  for 
union  with  os  pubis.  It  is  smooth,  both  externally  and 
internally  ;  externally,  in  forming  the  neck  of  the  ischium, 
over  which  obturator  internus  and  pyriformis  play,  the  latter 
muscle  is  attached  to  a  roughened  line  on  the  upper  part  of 
Ihe  process  ;  internally  in  forming  with  the  ant ero -internal 
process  an  arch  with  rounded  margin,  which  looks  forwards 
and  gives  attachment  to  obturator  externus,  and  assists  in 
forming  the  obturator  foramen.  The  anterior  extremity 
of  the  last-mentioned  process  joins  os  pubis,  while  its  inner 
margin,  meeting  its  fellow,  assists  the  corresponding  part 
of  the  body  in  forming  symphysis  ischii,  the  union  becom- 
ing strengthened  below  by  a  connecting  ligament,  particu- 
larly thick  opposite  the  posterior  margin  of  obturator 
foramen,  in  becoming  reflected  down  to  form  the  triangular 
■ligament  of  the  penis  of  the  male.  The  superior  margin  of 
(Symphysis  pubis  et  ischii  affords  attachment  along  almost 


OSTEOLOGY.  85 

its  whole  length  to  a  reflection  inwards  of  the  sacro-sciatic 
ligament,  which  covers  the  origin  of  obturator  internus 
from  the  superior  part  of  the  margins  of  the  foramen  of 
the  same  name,  separating  it  from  the  pelvic  viscera.  The 
posterior  2)rocess  of  the  ischium  is  triangular  and  tuberous  - 
at  its  extremity,  which  extends  outwards  and  backwards,, 
and  is  termed  the  tuberosity  of  the  ischium.  It  presents 
a  .small  rough  ridge,  extending  forwards  along  its  outer  ■ 
margin  to  the  neck,  from  which  ischio-femoralis  arises. - 
To  the  posterior  tuberous  part  triceps  abductor  femoris, 
biceps  rotator  tibialis,  ischio  tibialis  and  erector  penis  are 
attached.  The  inner  margin  of  this  process  slopes  inwards 
towards  its  fellow,  which  it  joins  at  an  oblique  angle  at  the 
symphysis.  This  is  the  ischial  arch,  and  round  it  the  urethra 
passes  from  the  pelvis  into  the  penis.  In  so  doing  it  is  bound  ■ 
down  by  a  small  ligament  and  by  the  crura,  which,  being 
attached  on  either  side,converge  to  form  corpus  cavernosum. 

OS  PUBIS  consists  of  three  sides  and  three  angles ;  its 
inner  margin  lies  in  contact  with  its  fellow,  and  thus  forms 
symphysis  pubis,  continuous  with  and  analogous  to  sym- 
physis ischii.  The  posterior  angle  is  united  to  the  antero- 
internal  process  of  the  ischium,  and  from  it  the  outer 
margin  forms  an  arch  running  forwards  and  outwards^ 
which,  after  completing  the  obturator  foramen,  terminates 
in  the  junction  with  os  ischium  and  os  ilium,  forming  the 
acetabulum.  The  anterior  margin,  forming  the  brim  of  the 
floor  of  the  pelvis,  is  at  first  smooth,  centrally  presents  a 
rough  prominence,  pectineal!  tubercle,  to  which  pectineus 
is  attached,  and  inwardly  these  two  pectinean  tubercles  are 
connected  by  a  dense  fibrous  band,  which  affords  attach- 
ment to  the  abdominal  muscles  anteriorly,  and  posteriorly 
is  partly  continuous  with  the  connecting  ligament  of  the 
symphysis,  while  the  rest  of  it  passes  through  a  groove, 
which  occupies  the  under  surface  of  os  pubis,  extending 
outwards  to  the  pubic  notch  of  the  acetabulum.  Sym- 
physis pubis  superiorly  forms  a  smooth  concave  surface  for 
the  bladder  to  rest  upon,  and  externally  to  this  the  inward 
reflection  of  the  sacro-sciatic  ligament  is  attached.  To  the' 
under  surface  of  the  whole  symphysis  the  common  tendon 
of  the  graciles  is  attached  centrally,  and  on  either  side  a 
biceps  adductor  femoris. 

The  FEMUR  is  a  long,  round  bone,  extending  from  the 
hip  to  the  stifle.     It  is  the  largest  bone  in  the  body,  and 


86  OUTLINES   OF   EQUINE   ANATOMY. 

centrally  is  rounded,  but  superiorly  becomes  flattened  from 
behind  forwards.  It  consists  of  a  sliaft  and  two  extremi- 
ties. Tlie  shaft  presents  four  surfaces.  The  anterior 
surface  is  in  all  parts  convex  and  rounded,  though  in  blend- 
ing with  the  upper  extremity  it  is  inclined  to  become  flat. 
It  is  directly  continuous  with  the  inner  and  outer  surfaces. 
The  inner  surface  is  rounded.  Supero-posteriorly  it  pre- 
sents a  roughened  prominence,  elongated  from  above  down- 
wards, continuous  by  two  roughened  sharp  lines  with  the 
head.  The  anterior  of  these  sharp  lines  marks  out  the 
attachment  of  vastus  iuternus.  This  prominence  is  tro- 
chanter minor  internus.  To  it  are  attached  psoas 
magnus  and  iliacus.  Below  it  the  surface  is  roughened 
for  attachment  of  pectineus  and  of  one  head  of  biceps 
adductor  femoris  ;  still  lower  down  is  an  oblique  smooth 
surface,  extending  from  above  downwards  and  backwards 
for  passage  of  the  femoral  artery  and  vein,  at  the  upper 
part  of  which,  opposite  the  centre  of  the  bone  postero- 
internally  is  the  medullary  foramen.  Still  lower  down  this 
surface  is  very  rough  for  attachment  of  the  other  head  of 
biceps  adductor  femoris.  The  jjosterior  surface  of  the  bone 
superiorly  is  very  wide,  j^resenting  a  fiat  surface  between 
the  two  small  trochanters.  Slightly  inclined  to  the  outer' 
side  of  the  centre  of  this  part  is  a  roughened  surface  for 
attachment  of  ischio-femoralis  and  a  portion  of  triceps 
abductor  femoris.  From  the  upper  part  of  trochanter 
minor  externus  a  thick  ridge  runs  upwards  towards  the 
posterior  part  of  trochanter  major;  this  forms  the  outer 
boundary  of  the  trochanteric  fossa,  a  deep  depression  on 
the  supero-posterior  and  external  part  of  the  bone,  into  which 
are  inserted  the  two  obturator  muscles  and  pyriformis, 
with  gemini  or  ischio-trochanterius.  The  middle  third 
of  this  surface  is  roughened  and  continuous  with  that  on 
the  inner  surf  ace  for  pectineus  and  biceps  adductor  femoris  ; 
below  this,  separated  by  the  smooth  oblique  groove  for  the 
femoral  artery,  is  a  triangular  space  extending  as  far  as 
the  outer  condyle  for  attachment  of  the  lower  head  of 
biceps  adductor  femoris.  The  external  surface  presents 
superiorly  the  ridge  running  from  trochanter  major  to 
trochanter  minor  externus,  to  which  the  posterior  head  of 
gluteus  maximus  is  attached.  This  culminates  in  a  long 
process  flattened  from  before  backwards,  curled  forwards, 
and  tuberous  at  its  free  margin,  trochanter  minor  externus, 


OSTEOLOGY.  87 

to  wliicli  gluteus  externus  is  attaclied.  Below  this  for  a 
short  distance  it  is  smooth,  and  still  lower  down  is  a  deep 
fossa  which  looks  outwards  and  backwards,  and  is  rough- 
ened for  attachment  of  gastrocnemius  internus.  It  is 
bounded  by  ridges,  of  which  the  outer  is  most  prominent 
and  roughened  for  origin  of  the  outer  head  of  gastrocne- 
mius externus ;  while  the  other  head  arises  from  near  the 
lower  insertion  of  biceps  adductor,  separated  from  the 
former  and  from  internus  by  the  femoral  artery.  The 
inner  ridge  is  smooth.  The  superior  extremity  is  divided 
into  two  parts — head  and  trochanter  major.  The  head 
IS  internally  placed,  and  consists  of  a  rounded  articular 
surface,  convex  in  every  direction,  with  a  break  in  its 
margin  at  the  internal  part,  which,  running  upwards,  leads 
into  a  deep  groove  extending  to  the  centre  of  the  head, 
roughened  for  attachment  of  ligamentum  teres  and  the 
pubio -femoral  tendon  of  rectus  abdominis.  Around  the 
outer  margin  of  this  surface  is  attached  the  capsular  liga- 
ment of  the  hip-joint.  From  the  head  outwards,  bounded 
posteriorly  by  the  trochanteric  fossa,  anteriorly  by  the 
dilated  upper  extremity  of  the  anterior  surface,  is  a  ridge 
of  bone,  which  externally  becomes  much  expanded  in  form- 
ing an  irregularly  concave  surface,  looking  inwards,  per- 
forated by  numerous  foramina,  to  which  gluteus  internus 
becomes  attached.  This  is  the  inner  surface  of  trochanter 
major,  which  consists  of  two  parts,  the  anterior  one 
rounded  and  rough,  presenting  on  its  external  surface 
centrally  a  smooth  spot  for  a  bursa,  below  which  is  a  ridge 
for  insertion  of  the  anterior  head  of  gluteus  maximus. 
The  ijosterior  ]jart  is  much  larger,  and  superiorly  presents 
a  roughened  extremity  for  attachment  of  another  head  of 
gluteus  maximus,  and  from  this  a  roughened  ridge  forming 
the  outer  boundary  of  the  trochanteric  fossa  runs  to  tro- 
chanter minor  externus,  to  which  ridge  the  third  head  of 
gluteus  maximus  is  attached.  At  the  smooth  surface  between 
trochanter  major  and  the  head  ilio-femoralis  is  attached  to 
a  thin  roughed  line  running  from  above  downwards. 
The  inferior  limit  of  trochanter  major  and  the  anterior 
margin  of  the  ridge  running  to  the  external  small  trochan- 
ter mark  out  the  superior  attachment  of  vastus  externus. 

The  inferior  extremity  of  the  femur  may  be  divided 
into  an  anterior  and  a  posterior  part.  The  anterior  con- 
sists of  two  articular  ridges,  which  look  downwards  and 


88  OUTLINES    OF   EQUINE   ANATOMY. 

forwards,  wliicli  form  a  continuous  articulatory  surface 
for  tlie  patella  to  play  over.  The  inner  is  mucli  tlie  largest, 
especially  suj^ero-anteriorly,  where  it  becomes  bulbous,  with 
an  inclination  inwards.  The  outer  decreases  slightly  in 
size  posteriorly.  The  non-articulatory  parts  of  these  ridges 
are  rough  for  attachment  of  the  capsular  ligament  of  the 
stifle.  The  ijosterior  part  of  the  inferior  extremity  consists 
of  two  condyles  separated  by  the  intercondyloid  fossa, 
which  runs  from  behind  forwards.  It  is  roughened  for 
attachment  at  its  postero-internal  part  of  the  postero- 
superior  ligament  of  the  outer  interarticular  disc  of  car- 
tilage. Just  in  front  of  this  the  outer  condyle  is  under- 
mined for  attachment  of  the  superior  extremity  of  one 
crucial  ligament,  while  the  inner  similarly  affords  attacil- 
ment  to  the  other.  Anteriorly  are  numerous  foramina. 
The  outer  condyle  is  the  largest,  and  in  front  of  its  inferior 
extremity  is  a  deep  depression,  whence  arises  the  common 
tendon  of  flexor  metatarsi  and  extensor  pedis.  Behind  an^ 
above  this  is  a  ridge  running  backwards,  to  the  anteria* 
part  of  which  the  tendon  of  popliteus  is  attached,  to  ths 
posterior  parts  the  outer  lateral  ligaments  of  the  patella, 
and  of  the  stifle  joint.  The  inner  surface  of  the  interna}, 
condyle  is  roughened,  and  presents  a  prominence  to  which 
are  attached  the  corresponding  inner  lateral  ligaments. 
The  articulatory  surface  of  the  inner  condyle  is  continuous 
with  that  of  the  inner  ridge. 

PATELLA  is  a  floating  bone,  situated  at  the  infero- 
anterior  part  of  the  femur.  It  is  the  "  knee  cap  "  of  the 
human  subject,  and  has  three  surfaces  and  three  angles. 
The  superior  surface  looks  slightly  backwards,  it  is  bicon- 
.cave  (slightly)  affords  attachment  to  triceps  cruralis,  and 
is  bounded  anteriorly  by  a  prominent  margin,  posteriorly 
by  a  line,  convex  externally,  concave  internally.  These 
meet  at  a  rounded  angle  outwardly,  from  which  run  the 
outer  patellar  lateral  and  straight  ligaments,  and  at  an  acute 
angle  inwards,  where  the  bone  is  continued  by  a  fibre -car- 
tilaginous prolongation,  from  the  extremities  of  which  pass 
the  inner  lateral  and  inner  sti'aight  patellar  ligaments.  The 
cmtenor  surface  is  rough  and  convex,  affording  attachment 
outwardly  to  triceps  abductor  femoris.  Its  superior  mar- 
gin is  rounded.  Its  inferior  margin  comes  to  a  point  cen- 
trally ;  just  above  this  is  a  smooth  spot  for  a  bursa  and 
still  higher  up  is  roughened  for  attachment  of  the  central 


OSTEOLOGY.  89 

straight  ligament.  Externally  to  this  is  the  attachment  of 
the  outer  straight  ligament.  The  posterior  surface  of  the 
bone  is  articulatory,  consisting  of  an  outer  small  part  con- 
nected by  a  broad  prominent  ridge  with  the  inner  large 
part,  which  superiorly  is  concave  and  extends  downwards, 
inferiorly  inclines  forwards,  terminating  internally  in  a 
point.  The  outer  part  plays  over  the  outer  ridge  of  the 
femur,  the  inner  over  the  inner  ridge,  the  surface  being 
completed  by  the  cartilaginous  prolongation  inwardly. 
Around  this  surface  the  capsular  ligament  is  attached  ex- 
ternally and  internally. 

The  TIBIA  is  a  long  round  bone  extending  from  the 
stifle  to  the  hock.  It  articulates  superiorly  with  the  femur 
through  the  medium  of  the  semilunar  discs  of  cartilage, 
and  directly  inferiorly  with  the  astragalus;  outwardly 
with  the  fibula.  It  consists  of  a  shaft  and  two  extremities. 
The  shaft  is  prismatic  presenting  three  surfaces,  antero- 
external,  antero-internal,  and  posterior.  The  anterior  sur- 
faces centrally  blend,  forming  a  rounded  margin,  but 
superiorly  become  expanded  and  unite  in  forming  a  sharp 
ridge,  which  increases  in  size  as  it  proceeds  upwards.  To 
the  internal  surface  of  this  ridge  the  expanded  tendinous 
layer  common  to  ischio-tibialis,  sartorius,  and  gracilis  is 
attached  along  its  whole  length,  while  biceps  rotator 
tibialis,  after  playing  over  a  bursa  on  this  sur- 
face is  attached  to  its  prominent  edge  about  the 
centre.  Along  the  sharp  anterior  margin  externally  is 
attached  the  aponeurosis  of  triceps  abductor  femoris, 
while  to  the  external  surface  of  the  ridge,  the  free  margin 
of  which  slightly  bends  outwards,  is  attached  the  muscular 
portion  of  flexor  metatarsi.  The  superior  extremity  of  the 
ridge  is  triangular,  bifurcating  in  forming  two  prominences 
separated  by  a  smooth  groove.  To  the  upper  part  of  these 
j)rominences  the  inner  aud  outer  straight  ligaments  of  the 
patella  are  attached.  While  the  central  straight  ligament, 
after  playing  over  a  bursa  situated  in  the  groove,  becomes 
attached  to  the  point  of  bifurcation.  The  inner  prominence 
is  much  the  largest.  The  antero-internal  surface  is  imme- 
diately subcutaneous,  and  over  it  runs  vena  saphena  from 
before  backwards  and  upwards.  The  anter  a -external  surface 
is  occupied  by  the  passage  of  flexor  metatarsi  and  extensor 
pedis  and  is  smooth.  Inferiorly  this  surface^  becomes 
wider  on  approaching  the  inferior  extremity  and  internally 


90  OUTLINES   OF   EQUINE    ANATOMY. 

it  presents  a  small  prominence  roughened  for  attacliment 
of  tlie  snpero-anterior  annular  ligament  of  the  liock, 
which  runs  obliquely  downwards  and  outwards,  over  the 
tendons  of  flexor  metatarsi  and  extensor  pedis  towards  the 
infero- external  part  of  the  hone.  The  j^osterior  surface 
is  divided  into  two  parts.  One  superiorly  placed,  bounded 
superiorly  by  the  superior  margin  of  the  bone,  internally 
by  the  superior  half  of  the  inner  margin,  externally  by  a 
line  running  from  without  inwards,  obliquely  downwards. 
These  enclose  a  triangular  space  to  which  popliteus  is 
attached.  The  rest  of  this  surface  is  roughened  by  ridges 
running  obliquely  inwards  and  downwards,  to  the  outer 
part  of  which  is  attached  flexor  pedis  perforans  to  the 
inner  flexor  pedis  accessorius  ;  these  two  muscles  are  sepa- 
rated by  the  posterior  tibial  artery,  which  runs  through  a 
smooth  groove,  which  at  the  inferior  part  of  the  superior 
third  of  this  surface  presents  the  medullary  foramen.  The 
inner  margin  of  the  bone  is  inferiorly  unoccupied.  Its 
superior  part  affords  attachment  to  popliteus  and  about  the 
centre  of  this  half  is  a  remarkable  prominence  serving  to 
mark  out  the  course  of  the  tendon  of  biceps  rotator 
tibialis.  Superiorly  this  margin  gives  attachment  to  the 
inner  lateral  ligament  of  the  stifle  joint.  The  oute^^  mar- 
gin superiorly  is  roughened,  affording  attachment  to  the 
outer  lateral  ligament ;  below  this  is  a  roughened  line  to 
which  the  upj^er  extremity  of  the  fibula  is  attached  by 
white  fibrous  tissue ;  below  this  a  smooth  surface  helping 
to  form  the  fibular  arch  through  which  the  anterior  tibial 
vessels  pass.  This  margin  as  far  down  as  the  inferior 
extremity  gives  attachment  to  the  white  fibrous  tissue 
which  connects  it  to  the  fibula.  Its  superior  part  is  sepa- 
rated from  the  anterior  ridge  of  the  bone  by  a  deep  smooth 
rounded  groove,  in  which  lies  a  bursa  for  passage  of  the 
tendon  common  to  flexor  metatarsi  and  extensor  pedis. 
Flexor  pedis  perforans  extends  as  far  up  as  the  posterior 
2:)art  of  the  expanded  superior  extremity  of  this  margin. 

The  superior  surface  of  the  bone  is  divided  into  two 
articular  surfaces  by  a  spine  which  runs  from  behind  for- 
wards, presenting  an  irregular  groove  extending  from  the 
perforated  line  which  separates  the  anterior  ridges  from 
this  superior  surface,  to  the  posterior  margin.  It  is  rough 
and  prominent,  anteriorly  affording  attachment  to  one  of 
the  crucial  ligaments,  and  to  the  anterior  ligaments  of  the 


OSTEOLOGY.  91 

semilunar  cartilages.  Beliind  this  it  is  concave  and  per- 
forated, affording  attachment  to  the  posterior  ligament  of 
the  inner  cartilage,  while  to  its  junction  with  the  posterior 
margin  are^  attached  the  postero -inferior  ligament  of  the 
outer  cartilage  and  the  other  crucial  ligament.  The  inner 
side  of  the  spine  is  by  far  the  most  prominent,  and  its 
external  surface  is  articulatory  continuous  v/ith  the  inner 
articulator y  facet,  which  is  ovoid,  bounded  by  a  roughened 
margin  and  lying  in  contact  with  the  under  surface  of  the 
inner  cartilage  and  with  the  inner  condyle  of  the  femur. 
The  outer  articulatory  surface  is  triangular,  concave,  and 
looks  slightly  backwards,  and  is  in  contact  with  the  under 
surface  of  the  outer  cartilage  and  with  the  outer  condyle. 
The  inferior  extremity  is  c^uadrilateral  and  consists  of  two 
articular  grooves  running  obliquely  from  within  outwards 
and  forwards,  which  come  in  contact  with  the  sujDcrior 
articulatory  surface  of  astragalus.  The  inner  groove  is  the 
deepest  and  the  narrowest  and  extends  farthest  backwards. 
The  outer  in  some  cases  consists  of  two  portions  of  bone  con- 
nected by  fibrous  tissue,  tlie  outer  of  tJiem  being  the  inferior 
extremity  of  the  fibula.  The  outer  margin  is  rough  and  pro- 
minent, being  termed  the  outer  malleolus,  over  which  a 
groove  for  peroneus  runs  downwards.  It  affords  attach- 
ment to  the  capsular,  outer  lateral  and  supero-anterior 
annular  ligament  of  the  hock.  The  ijosterior  margin  is 
rough  for  attachment  of  the  capsular  ligament,  and 
comes  to  a  point  centrally.  The  inner  margin  is 
rough,  and  posteriorly  presents  a  groove  running 
from  above  downwards  for  flexor  pedis  accessorius, 
anteriorly  the  internal  malleolus,  larger  than  the  outer, 
which  gives  attachment  to  the  inner  lateral  and  capsular 
ligaments.  The  anterior  margin  is  straight,  and  rough  for 
attachment  of  the  capsular  ligament. 

The  FIBULA  is  a  small  very  much  elongated  piece 
of  bone,  situated  at  the  external  part  of  the  tibia, 
rounded  for  the  most  part  and  by  its  inner  part  con- 
nected with  the  tibia  by  white  fibrous  tissue,  some- 
times continued  as  far  as  the  true  hock  joint.  Some- 
times its  middle  part  degenerates  into  a  white 
fibrous  band.  Superiorly  it  slightly  expands  in  forming 
a  button-like  extremity  flattened  from  without  inwards, 
the  inner  surface  of  which  is  roughened  for  attachment 
of  white  fibrous  tissue  connecting  it  to  the  suj)ero- external 


92  OUTLINES    OF    EQUIN'E    ANATOMY. 

part  of  the  tibia.  Below  this  the  surface  (internaT)  is- 
smooth,  forming  (with  the  tibia)  the  fibular  arch  through 
which  the  anterior  tibial  vessels  pass.  The  external  sur- 
face of  the  button-like  superior  extremity  is  occupied  by 
the  attachment  of  the  outer  lateral  ligament  of  the  patella. 
The  greater  part  of  fhe  remainder  of  the  external  surface 
gives  attachment  to  peroneus. 

TARSUS,  HOCK  (ANKLE  OF  HUMAN  SUBJECT), 

consists  of  a  number  of  small  bones  resembling  to  a  certain 
extent  those  of  the  knee.  It  occupies  the  space  between 
the  tibia  and  the  metatarsus,  and  consists  of  two  roivs  of 
hones,  of  which  the  superior  is  formed  by  two  somewhat 
large  bones,  astragalus  and  calcis,  while  the  inferior  con^ 
sists  of  four  smaller  bones,  and  is  split  into  two  rows  on 
its  inner  side,  so  that  while  cuboides  occupies  the  whole 
depth  of  the  row  on  the  outer  side,  cuneiforme  magnum 
forms  the  upper  and  cuneifoiTae  medium  and  parvum 
f  oi-m  the  lower  subdivision  on  the  inner  side.  It  is  between 
these  bones  on  the  inner  side  that  "  spavin  "  generally 
first  manifests  itself. 

OS  CALCIS  is  the  postero-external  bone  of  the  upper 
row,  and  articulates  by  three  facets  anteriorly  mth  astra- 
galus, inferiorly  with  cuboides.  It  consists  of  a  hocly  and 
a  process.  The  hodij  consists  of  a  large  portion  externally 
placed,  which  presents  externally  a  roughened  surface  to 
which  ligaments  are  attached.  Internally  a  very  irregular 
aspect,  having  at  its  postero-inferior  part  a  somewhat 
square  projection  which  superiorly  is  roughed  for  attach- 
ment of  the  capsular  ligament  of  the  hock,  posteriorly  has 
a  groove  coated  with  fibro  cartilage,  over  which  flexor  pedis 
perforans'plays,  internally  and  inferiorly  roughened  surfaces 
for  ligamentous  attachment.  Anteriorly  a  slightly  concave 
oblong  aiiiculatory  facet  extending  from  above  down- 
wards obliquely  inwards  for  articulation  with  astragalus. 
The  main  portion  of  the  body  just  above  this  process  on 
the  inner  surface  presents  a  small  elongated  facet  looking 
upwards,  inwards,  and  forwards,  which  is  continuous  round 
an  acute  articular  margin  with  another  facet  looking 
downwards  and  slightly  forwards.  The  rest  of  the  inner 
surface  running  to  a  point  inferiorly  is  roughened  for 


OSTEOLOGY.  93 

attacliment  of  interosseous  ligaments.     Along  tlie  anterior 
margin  may  be  seen  a  small  facet  looking  inwards,  con- 
tinuous with  a  large  one  upon  the  margin  looking  forwards, 
the  rest  of  this  margin  is  rough.     The  inferior  margin  is 
mainly  occupied  by  an  irregular  slightly  concave  articu- 
latory  surface  for  os  cuboides,  this  is  continued  slightly 
on  to  the  internal  surface  at  its  inferior  point  as  a  small 
facet  for  union  with  astragalus.     From  the  siq^erior  mar- 
gin the  process  runs   upwards.     The  loosterior  margin  is 
continuous  with  the  posterior  margin  of  the  process  and 
both  are  rounded   and  roughened  for  attachment  of  the 
€alcaneo- cuboid  ligament.     The  sujjerior  extremity  of  the 
process  is  tuberous,  slightly  inclined  forwards.     Anteriorly 
it  presents  a  smooth  surface  for  a  bursa,  over  which  gastro- 
cnemius extemus  plays,   becoming   inserted   just   behind, 
while   still   farther    back   this   surface  is  smooth  for  the 
bursa  situated  on  the  point  of  the  hock,  where  the  expanded 
tendon  of  gastrocnemius  internus  forms  a  cap  for  it,  be- 
coming attached  by  a  fibrous  band  running  to  the  process 
on  either  side.     The  anterior  margin  is  thinner  than  the 
posterior   but   rounded.     The  external    surface  is   subcu- 
taneous.    The  internal  surface  coated  with  fibro-cartilage, 
continuous  with  that  on  the  oblique  posterior  part  of  the 
inner  prommence  of  the  body,  over  which   the  perforans 
tendon  plays,  bound  down  by  the  posterior  annular  ligament. 
OS  ASTRAGALUS  is  a  square  bone  at  the  inner  part  of 
the  upper  row  of  the  hock  bones.     It  articulates  superiorly 
with   the    tibia,   posteriorly   with   calcis,    inferiorly   with 
cuneiforme  magnum  and  cuboides.  It  has  five  surfaces.  The 
antero-superior  surface  presents   two   prominent   rounded 
articular  ridges,  running  obliquely  downwards  and  out- 
wards.    The  inner  ridge  is  the  longest,  and  its  inner  side 
the  straightest,  and  completely  coated  with  cartilage.     It 
extends  beyond  the  outer,  both  anteriorly  and  posteriorly. 
The   outer   ridge   curls   slightly    outwards   at   its   inferior 
extremity,  and  is  separated  from  the  inner  by  a  deep  syno- 
vial fossa,  which  is  shorter  than  either  of  the  grooves,  and 
generally  presents  a  break  in  the  articular  cartilage  cen- 
trally.    Between  it,  the  grooves,  and  the  inferior  surface, 
is    a    triangular  depression,    roughened    for   attachment 
of   extensor    pedis    accessorius.     The  ]}osterior  surface  of 
the  bone   is    extremely  irregular.     Internally  it  presents 
superiorly  a  roughened  prominence,  and  below  this   the 


94  OUTLINES    OF   EQUINE   ANATOMY. 

posterior  surface  of  the  tubercle.  More  outwardly,  sepa- 
rated from  tlie  ridge  by  a  deep  perforated  fossa,  is  an 
ovoid  articulately  surface  for  os  calcis,  extending  directly 
downwards  ;  and  more  outwards,  inclined  to  the  outer  sur- 
face and  extending  obliquely  forwards,  is  an  articulatory 
facet  consisting  of  two  parts,  one  of  wbicb  is  vertical,  the 
other  horizontal.  A  little  lower  down,  on  the  outer  side,  is 
another  small  facet,  elongated  from  above  downwards.  We 
see  a  third  at  the  inf  ero-external  angle  of  the  bone  con- 
tinuous with  that  on  the  inferior  surface  of  the  bone.  The 
interarticular  space  is  rough  and  perforated.  The  outer  sur- 
face is  small,  rough,  and  concave,  giving  attachment  to  one  of 
the  lateral  ligaments.  The  inner  surface  is  roughened  and 
flat  superiorly,  inferiorly  forms  a  prominent  tubercle  ;  to- 
the  whole  of  it  ligamentous  substance  is  attached.  The  an- 
terior margm  of  both  the  inner  and  outer  surfaces  is  occupied 
by  the  outer  margin  of  the  supero- anterior  articular  ridges. 
The  inferior  surface  is  mainly  articulatory,  consisting  of  a 
slightly  convex  surface,  elongated  from  side  to  side,  ex- 
ternally continuous  with  a  small  triangular  facet  for  os 
cuboides,  which  is  continuous  with  one  on  the  posterior 
part  for  os  calcis.  Anteriorly  it  almost  reaches  the  internal 
ridge,  and  at  the  under  surface  of  the  tubercle  is  reflected 
backwards,  extending  to  about  the  centre  of  the  posterior 
part  of  the  bone,  where  it  terminates  in  becoming  continu- 
ous with  the  inner  articulatory  facet  for  os  calcis  of  the 
posterior  part.  The  anterior  and  reflected  portions  are 
separated  by  a  gap  in  the  articular  cartilage,  which  presents 
numerous  foramina.  This  portion  internally  is  more  con- 
cave than  the  rest  of  the  surface,  being  separated  from  its 
outer  extremity  by  a  prominent  point.  This  large  articu- 
latory surface  comes  in  apposition  with  cuneif orme  magnum. 
OS  CUNEIFORME  MAGNUM  is  a  flat  bone  with  two 
surfaces  and  four  margins.  The  sujyerior  surface  is  concave 
in  most  parts,  and  is  prominent  at  the  outer  j^art  of  its 
anterior  margin.  It  is  the  exact  counterpart  of  the  infe- 
rior extremity  of  astragalus  (with  exception  of  its  small 
surface  for  os  cuboides),  and  therefore  requires  no  detailed 
description.  Its  posterior  part  is  most  prominent,  espe- 
cially inwardly ;  inferiorly  it  articulates  with  ossa  cunei- 
forme  parvum  and  medium.  For  medium  it  presents  a 
large  articulatory  surface,  extending  along  the  anterior 
border,  having  a  convex  anterior,  concave  posterior  margin 


OSTEOLOGY.  95 

almost  flat,  witli  its  inner  and  larger  half  inclined  slightly 
inwards.  At  the  postero- external  angle  is  another  facet 
for  mediuna,  which  is  rounded,  slightly  concave,  continuous 
with  a  small  facet  on  the  outer  margin  at  the  posterior  part 
for  OS  cuboides.  For  parvum  there  are  two  small  round 
facets,  continuous  with  each  other  at  the  antero-internal 
angle,  the  outer  being  concave,  almost  continuous  with  the 
anterior  surface  for  medium,  the  inner  convex  looking 
downwards  and  backwards.  The  rest  of  this  surface  is 
extremely  rough  for  attachment  of  interosseous  liga- 
ments;  in  some  places  it  is  perforated  by  foramina. 
The  miteriov  and  internal  margins  of  the  bone  are  rough- 
ened for  attachment  of  ligaments,  and  the  imsterior  margin 
presents  two  very  irregular  prominences  separated  by  an 
irregular  groove,  which  is  continuous  with  the  roughened 
groove  upon  the  inferior  surface.  The  posterior  surface 
for  articulation  with  cuneiforme  parvum  encroaches  upon 
the  inner  prominence  below.  The  outer  prominence  inclines 
slightly  outwards,  and  on  its  postero-external  part  presents 
a  concavo-convex  surface,  extending  obliquely  upwards  and 
backwards  for  union  with  os  cuboides.  In  connection  with 
the  external  extremity  of  the  anterior  articulatory  part  of 
the  upper  surface  is  a  facet  elongated  from  before  back- 
wards, also  coming  into  connection  with  os  cuboides. 
Behind  this  is  a  groove  extending  upwards  and  backwards 
to  the  break  in  the  superior  surface.  The  rest  of  the 
surface  is  rough  for  attachment  of  interosseous  ligaments. 
CUNEIFORME  MEDIUM  is  a  flat  bone,  situated  at  the 
lower,  inclined  to  the  inner,  part  of  the  hock.  It  may  be 
distinguished  from  cuneiforme  magnum  by  a  projection 
from  the  centre  of  its  posterior  margin,  which  is  inclined 
slightly  inwards.  The  u])jper  surface  is  for  the  most  part 
articulatory,  presenting  two  distinct  facets  for  union  with 
magnum.  The  first  is  oblong  with  a  notch  in  its  posterior 
margin.  It  presents  an  anterior  and  a  posterior  rounded 
margin ;  the  surface  slants  from  the  former  to.  the  latter ; 
it  is,  therefore,  concave.  The  posterior  notch  is  separated 
by  a  roughened  perforated  space  from  an  ovoid  facets 
extending  obliquely  inwards  on  the  superior  surface  of  the 
process.  The  under  surface  much  resembles  this,  but  the 
articulatory  facets  are  convex  and  less  regular,  and  the 
posterior  facet  is  elongated  from  side  to  side,  inclining  out- 
wards and    backwards,   also   the    intervening  roughened 


96  OUTLINES    OF    EQUINE    ANATOMY. 

space  is  larger.  It  articulates  with  os  metatarsi  inagnum, 
and  posteriorly  with  the  inner  splint  bone.  The  anterior 
margin  is  convex,  most  prominent  along  its  central  line, 
and  on  the  inner  side,  near  both  the  upper  and  the  lower 
surfaces  are  rows  of  foramina.  The  inner  margin  is  a 
deep  groove,  the  sides  of  which  meet  at  an  oblique  angle. 
It  is  everywhere  roughened,  except  at  its  antero-iuferior 
angle,  where  is  a  small  articulatory  surface  for  union  with 
cuneifonne  parvum.  The  external  margin  presents  a  shal- 
lower groove  than  the  internal,  and  a  larger  articulatory 
surface  at  the  antero-inferior  part  for  cuboides.  The 
posterior  angle  at  w^hich  these  two  surfaces  meet  looks 
obliquely  downwards  and  backwards,  being  prolonged  su- 
periorly into  a  very  thin  process,  with  the  superior  part  of 
which  cuneiforme  magnum  articulates,  and  os  cuboides 
with  the  external  lateral  part. 

CUNEIFORME  PARVUM  is  situated  at  the  postero- 
internal and  inferior  part  of  the  hock.  It  has  two  surfaces 
and  a  process.  The  superior  surface  is  mainly  occupied 
by  a  smooth  concave  articulatory  surface  looking  inwards, 
bounded  anteriorly  by  a  roughened  ridge,  for  articulation 
with  magnum.  The  inferior  surface  presents  three  articu- 
latory facets.  The  posterior  facet  is  ovoid  and  distinct, 
and  articulates  with  the  inner  small  metatarsal  bone,  as 
also  does  the  central  facet,  which  is  continuous  with  the 
anterior  facet  for  metatarsi  magnum,  and  that  in  its  turn 
with  a  small  surface  for  medium  on  the  antero-internal 
part  of  the  bone.  The  process  is  continued  from  the 
posterior  margin,  is  flat  from  side,  tuberous,  has  rounded 
margins,  and  curls  inwards.  It  is  roughened  externally 
for  attachment  of  ligamentous  structure  (especially  a  band 
running  to  os  cuboides)  as  are  also  the  interarticular 
spaces.  The  roughened  depression  on  the  inferior  surface 
is  sometimes  so  deep  as  to  divide  the  bone  into  two  dis- 
tinct parts. 

OS  CUBOIDES  occupies  the  outer  part  of  the  lower 
row  of  hock  bones,  and  is  equal  in  thickness  to  the  sum 
of  the  two  cuneiforme  bones  (magnum  and  medium). 
This  thickness  is  characteristic,  and  serves  to  distinguish 
this  from  all  other  bones  except  os  scaphoides  of  the 
knee,  from  which  it  may  be  distinguished  by  the  greater 
number  and  the  smaller  size  of  its  articulatory  surfaces.  It 
has  six  surfaces.     The  anterior  smd  j)osterior  are  roughened 


OSTEOLOGY.  97 

for  ligamentous  attacliment,  more  especially  the  anterior 
for  the  middle  anterior  annular  ligament  for  which  there 
is  a  slight  depression.  The  external  surface  presents  a 
groove  running  from  below  upwards,  separating  the  rough- 
ened anterior  and  posterior  parts.  This  leads  upwards  to  a 
roughened  line  which  tends  to  separate  the  upper  surface 
into  two  articulatory  parts  and  after  reaching  the  inner 
surface  curves  in  a  direction  backwards.  Thus  at  the  pos- 
tero-external  angle  it  cuts  off  a  convex,  ovoid  facet  sloping 
obliquely  downwards,  outwards,  and  forwards  for  union 
with  OS  calcis.  The  anterior  articulatory  facet  is  divided 
into  two  parts,  the  outer  largest,  quadrilateral  at  the 
antero-external  angle  of  the  surface,  slanting  slightly 
outwards  and  forwards,  continuous  along  its  internal 
margin  with  the  inner  part  which  is  pyriform  (broadest 
posteriorly)  for  union  with  astragalus.  It  does  not  reach 
to  the  anterior  margin  of  the  bone,  but  along  its  inner 
edge  blends  with  a  pyriform  facet,  with  its  base  anteriorly 
placed  at  the  antero- superior  angle  of  the  internal  surface 
for  cuneiforme  magnum.  The  inter^ial  surface  at  its 
postero- central  part  has  a  prominence,  smooth  and  articu- 
latory both  above  and  below.  The  superior  facet  looks 
upwards  and  inwards  meeting  os  cuneiforme  magnum. 
The  inferior,  downwards  and  inwards  for  cuneiforme 
medium.  At  the  antero-inferior  angle  is  a  facet  elongated 
from  before  backwards  continuous  with  one  for  metatarsi 
magnum  on  the  inferior  surf  ace,  it  articulates  with  medium. 
The  space  between  these  is  roughened  for  ligamentous 
attachment,  but  around  the  posterior  and  superior  part  of 
the  last  mentioned  facet  is  a  deep  smooth  groove  extending 
to  below  the  articulatory  prominence  posteriorly,  through 
which  the  communicating  branches  between  the  anterior 
and  posterior  tibial  veins  run.  The  inferior  surface  presents- 
two  facets,  one  at  the  antero-external  angle,  the  other  at 
the  postero- external  angle  for  union  with  os  metatarsi 
parvum  externum.  The  former  is  largest  and  continuous 
inferiorly  with  a  surface  sloping  upwards  and  inwards  for 
metatarsi  magnum,  which  joins  one  on  the  inner  surface 
for  cuneiforme  medium.  The  superior  surface  is  occupied 
by  a  smooth  articulatory  surface  elongated  from  before 
backwards  with  the  greater  portion  of  which  os  calcis 
comes  in  contact. 

The  remainder  of  the  bones  of  the  hind  limb  resemble 

7 


98  OUTLINES    OF    EQUINE    ANATOMY. 

tlie  corresponding  bones  of  the  fore,  thongli  each  presents 
certain  points  of  difference  which  will  be  noticed. 

OS  METATARSI  MAGNUM  differs  from  the  large  meta- 
carpal hone. — In  being  about  one  and  one-third  times  as 
long,  in  being  rounder,  in  having  the  articular  surfaces  for 
the  splint  bones  more  posteriorly  placed.  In  a  tendency 
to  the  production  of  a  sharp  ridge  running  from  the  upper 
surface  of  the  bone  downwards  over  the  central  line  of 
of  the  antero-superior  part.  In  the  arrangements  of  its 
upper  surface,  which  presents  two  distinct  articulatory 
surfaces,  one  anteriorly  crescent-shaped,  one  posteriorly 
placed  rounded.  These  are  separated  by  a  roughened 
groove.  Supero-externally  is  a  groove  running  obliquely 
downwards  and  backwards  for  the  metatarsal  artery. 

OS  METATARSI  PARVUM  EXTERNUM  is  much  the 
largest  of  the  four  splint  bones.  Its  upper  extremity 
presents  at  the  antero-external  part  a  facet  for  os  cuboides, 
but  the  rest  of  this  extremity  which  is  rough  and  tuberous 
as  well  as  its  size  renders  it  readily  distinguishable. 

OS  METATARSI  PARVUM  INTERNUM  is  distin- 
guishable by  its  upper  extremity,  which  has  two  articu- 
latory facets  (continuous  with  that  for  union  with  os 
metatarsi  magnum)  for  os  cuneif orme  parvum,  and  one  on 
its  outer  side  for  cuneiforme  medium.  These  facets  with 
the  rest  of  the  surface  which  is  rough,  render  the  extreme 
upper  part  somewhat  pointed. 

OS  SUFFRAGINIS  is  larger  at  its  superior  extremity, 
smaller  at  its  inferior  than  that  of  the  fore  limb. 

OSSA  SESAMOIDEA,  OS  CORON-ffi  present  no  marked 
difference  ;  OS  NAVICULARE  is  smaller. 

OS  PEDIS  may  be  distinguished: — By  the  slight  ob- 
liquity of  its  antero-lateral  surface ;  by  the  greater  con- 
cavity, less  circular,  more  regularly  semilunar  shape  of 
its  plantar  surface,  which  is  widest  at  the  toe  and  gradually 
decreases  in  size  towards  the  heels,  while  that  of  the  fore 
limb  present  an  indentation  into  the  central  part  of  its 
posterior  crescentic  margin. 


AETHEOLOGY.  99 


PART  III— ARTHROLOGY. 

Articulations  are  tlie  unions  of  the  component  parts 
of  the  basement  structures,  the  means  by  which  such  parts 
are  enabled  to  play  on  one  another  in  adaptation  to  the 
various  movements  of  the  individual.  These  are  of  three 
kinds,  moveable,  imrtially  moveable,  and  fixed.  The  fixed  or 
synarthrotic  joints  are  those  which  in  the  young  animal 
are  moveable,  but  become  obliterated  later  on  in  life  ;  they 
mainly  serve  for  connection ;  motion  between  the  parts 
forming  them  is  but  slight,  it  is  impossible  after  full 
development  of  the  bones.  They  are  of  four  hinds,  the  most 
marked  examples  of  which  may  be  found  in  the  cranium. 
They  consist  of  the  coaptation  of  edges  or  surfaces  of 
bones  with  the  intervention  only  of  periosteum.  The  sim- 
plest forms  afford  the  most  firm  centres  of  connection. 

Sutura  is  the  apposition  of  two  edges  or  surfaces,  more 
or  less  complete,  by  the  adajDtation  of  prominences  on  one 
piece  to  depressions  on  the  other.  This  adaptation  may  be 
by  the  juxtaposition  of  irregular  surfaces,  sutura  squamosa, 
which  may  be  more  or  less  rough  ;  examples  of  this  may 
be  seen  in  the  union  of  the  malar  with  the  frontal  bone  ; 
or  it  may  be  by  the  dovetailing  of  two  jagged  edges,  sutura 
serrata  vel  dentata.  The  latter  name  is  applied  when  the 
jagged  margins  resemble  the  line  formed  by  the  edges  of  a 
dog's  molars. 

Harmonia  is  the  apposition  of  two  edges  of  bone,  which 
may  be  roughened,  but  are  not  jagged ;  they  therefore 
simply  are  in  contact,  and  connection  between  the  bones  is 
simply  by  continuity  of  periosteum,  as  in  the  union  between 
two  ossa  nasi. 

Gompliosis  is  the  insertion  of  a  peglike  process  of  one 
l>one  into  a  corresponding  cavity  of  another.  It  is  rare  ; 
the  connection  of  the  teeth  with  the  jaws  and  of  the  rib 
with  its  cartilage  are  examples. 

Schindylesis  is  the  union  of  three  l)ones,  by  the  attach- 


100  OUTLINES    OF    EQUINE    ANATOMY. 

ment  of  the  edge  of  one  Lone  into  a  groove  formed  by  part 
of  the  edges  of  the  others,  the  rest  of  the  union  between 
the  other  two  being  by  suture.  Such  is  the  attachment  of 
the  vomer  to  the  palatine  processes. 

Partially  moveable  or  ampMarthrotic  joints  are  those 
which,  while  admitting  a  small  amount  of  motion,  also 
afford  firm  union.  This  is  brought  about  by  insertion 
betv^een  two  roughened  surfaces  or  edges  of  bone  of  a  piece 
of  fibro -cartilage,  the  perichondrium  of  which  is  con- 
tinuous with  the  periosteum  of  the  bones  connected. 
Sooner  or  later,  in  different  individuals,  the  cartilage 
becomes  ossified  and  the  union  complete.  Such  is  the 
connection  of  the  ossa  innominata  by  means  of  the  sym- 
physis, and  of  the  two  halves  of  the  inferior  maxilla, 
which  "  grow  together,"  forming  the  symphysis  inferioris 
maxillae.  In  the  case  of  the  articulations  between  the 
bodies  of  the  vertebrae  we  see  permanent  amphiarthrotic 
joints.  Some  of  these  joints  are  strengthened  by  connecting 
ligaments. 

Diarthrotic,  synovial,  or  freely  moveable  joints  are  those 
in  which  the  component  parts  glide  more  or  less  upon  each 
other.  They  present  cavities  lined  by  synovial  membranes, 
the  surfaces  of  the  bones  in  apposition  are  coated  with 
articular  cartilage,  and  are  maintained  in  apposition  by 
ligaments.  These  ligaments  may  be  interosseous,  situated 
between  the  bones,  running  from  a  roughened  spot  on  the 
surface  of  one  bone  to  a  corresponding  part  of  its  fellow ; 
examples  may  be  seen  between  many  of  the  bones  of  the 
hock  and  knee  ;  connecting,  running  from  the  outer  surface 
of  one  bone  to  that  of  the  other.  Capsular,  broad,  expanded 
bands  of  white  fibrous  tissue  serving  to  strengthen  and 
protect  the  synovial  membranes  of  a  diarthrodial  joint. 
Annular,  extending  round  a  complex  joint  attached  to  all 
the  prominent  bony  points  it  presents,  keeping  in  position 
its  surrounding  structures  ;  generally  consists  of  a  broad 
ligamentous  expansion,  sometimes  simply  of  a  small  white 
fibrous  band  ;  examples  of  both  these  forms  may  be  seen  in 
the  hock.  The  motion  between  synovial  surfaces  may  be 
simply  an  almost  imperceptible  gliding ;  where  this  is  the  case 
the  joint  is  arthrodial.  Others  admit  of  more  or  less  exten- 
sive motion  in  two  ways — either  abduction  and  adduction 
(motion  from  or  towards  the  longitudinal  vertical  plane  of 
the  body),  or  elevation  and  depression  (motion  to  or  from 


ARTHROLOGY.  101 

the  ground  surface).  These  are  gin glymoid  joints,  and  in 
them  motion  may  be  limited  by  bony  in'ominences  sooner 
or  later  in  either  direction  ;  the  elbow-joint  is  an  apposite 
example.  Axonoides  or  pivot-like  motion  is  motion  on  the 
longitudinal  axis  of  the  joint,  as  ginglymus  is  on_  the 
transverse  axis ;  the  union  between  atlas  and  axis  is  of 
this  nature.  Rotatorial  or  ball-and-socket  joints  allow 
flexion,  extension,  abduction,  and  adduction,  axonoidal 
motion,  and  circumduction  (whereby  the  above  movements 
are  manifested  in  combination)  ;  examples  are  the  hip  and 
shoulder- joints,  in  which  a  more  or  less  globular  head  fits 
into  a  corresponding  cavity.  Joints  are  by  no  means  con- 
stant ;  thus  sometimes  a  small  synovial  sac  may  be  found 
in  the  centre  of  a  symphysis  ;  some  bones  are  united  together 
by  two  kinds  of  joints;  thus  most  of  the  vertebrae  are 
united  to  their  fellows  both  by  amphiarthrosis  and  by 
diarthrosis. 

The  ARTICULATIONS  OF  THE  HEAD  are  synarthro- 
dial  with  few  exceptions.  They  present  every  variety  of 
this  class,  while  the  petrous  temporal  bone  and  os  hyoides 
are  united  by  amphiarthrosis,  and  the  upper  to  the  lower 
jaw  by  diarthrosis.  The  latter  only  presents  unusual 
characters. 

Temporo-maxillary  articulation  is  the  apposition  and 
connection  of  the  glenoid  cavity  of  the  scjuamous  temporal 
bone  with  the  condyle  of  the  inferior  maxilla.  In  birds 
there  is  an  intervening  bone,  OS  qnadratum,  but  in  mam- 
malia this  is  only  represented  by  an  inter- articular  disc  of 
fihro -cartilage,  which  serves  to  separate  the  cavity  of  the 
joint  into  two  distinct  parts,  each  lined  by  a  synovial  mem- 
brane, so  that  both  surfaces  of  this  cartilage  are  lubricated 
by  synovia.  It  is  a  flattened  piece  of  cartilage,  elongated 
from  side  to  side,  and  all  around  its  outer  margin  is 
attached  the  capsular  ligament  of  the  joint,  which  extends 
from  the  outer  circumferent  margin  of  the  glenoid  cavity 
to  that  of  the  condyle.  It  is  strengthened  by  £i  fibrous  hand 
running  from  the  outer  part  of  the  condyle  to  the  outer 
part  of  the  cavity,  and  by  another  running  from  the  pos- 
terior part  of  the  condyle  to  the  mastoid  process  of  the 
squamous  temporal  bone,  and  continued  from  this  up  to 
the  base  of  the  external  auditory  process,  covering  a  small 
synovial  cavity.  This  joint  internally  is  covered  by 
pterygoideus,  externally  by  masseter  externus. 


lO'Z  OUTLINES    OF   EQUINE   ANATOMY. 

In  examining  tlie  synarthrodia!  articulations  of  the  skull 
we  notice  several  sutures,  one  of  whicli  divides  the  bone 
into  two  parts  longitudinally,  only  noticeable  superiorly 
and  not  extending  to  the  posterior  extremity  ;  this  is  the 
saggittal  suture  between  the  nasal,  frontal,  and  parietal 
bones  of  the  two  sides  of  the  head,  forming  the  "  plume  "  of 
the  arrow  posteriorly  between  the  parietal  and  triquatral 
bones.  Other  sutures  serve  to  mark  the  division  of  the 
skull  into  four  vertebral  segments  ;  they  are  the 

Lambdoidal,  between  os  occipitis  and  os  parietale,  so 
called  from  its  likeness  to  the  Greek  lambda  (A),  which  is 
caused  by  protrusion  of  the  mastoid  ridge  of  the  petrous 
temporal  between  these  two  bones. 

Coronal,  between  the  frontal  and  parietal  bones. 

Great  transverse,  between  the  frontal  and  nasal,  malar, 
lachrymal  bones,  extending  into  the  orbit.  All  these 
extend  downwards  on  either  side  towards  the  base  of  the 
skull. 

Atloido -occipital  articulation 

is  the  union  of  the  condyles  of  the  occiput  with  the 
anterior  ai*ticulatory  surfaces  of  the  atlas.  Each  of  these 
condyles  has  a  proper  synovial  membrane,  and  the  two  lie 
together  on  their  inner  and  inferior  parts.  Their  outer 
surfaces  are  strengthened  by  accessor}/  fih-es,  which  are  con- 
tinued superiorly,  extending  from  the  anterior  margins  of 
the  laminae  of  the  Atlas  to  the  superior  part  of  foramen  mag- 
num of  the  occiput,  forming  the  capsular  ligament.  Two  flat, 
white,  fibrous  bands  extend  from  the  styloid  processes  of  the 
occiput  to  the  anterior  margins  of  the  laminae.  This  joint 
is  ginglymoid,  admitting  motion  upwards  and  downwards. 

Atlo-axoid  articulation 

is  the  union  of  the  posterior  part  of  the  body  of  the  atlas 
and  the  posterior  part  of  its  superior  surface  with  the 
under  surface  of  the  odontoid  jDrocess,  and  its  antero-lateral 
continuations  on  the  dentata.  These  have  one  synovial 
membrane  attached  to  the  outer  circumferent  margin  of 
both  surfaces.  Inferiorly  along  the  central  line  this  is 
strengthened  by  a  small  band  of  yellow  elastic  tissue  (a  con- 
tinuation of  the  inferior  vertebral  ligament).  Laterally  it 
has  accessory  fibres,  which  are  continued  upivards,  connecting 
the  anterior  laminal  margin  of  the  axis  with  the  posterior 


ARTHHOLOGY.  103 

laminal  margin  of  the  atlas.  The  superior  spinous  process 
of  the  dentata  is  connected  to  the  upper  surface  of  the 
laminae  of  the  atlas  by  yellow  elastic  hands  lying  together 
along  the  middle  line  expanded  in  becoming  blended  with 
the  interlaminal  ligament  outwardly.  The  superior  surface 
of  the  synovial  membrane  is  in  contact  with  the  odontoid 
lig^aments,  three  in  number : — The  hroad  ligament  runs 
from  the  transverse  ridge  on  the  upper  surface  of  the 
odontoid  process,  the  two  small  ligaments  are  beneath 
this  just  visible,  one  on  either  side,  running  from  the 
depressions  on  the  upper  surface  of  the  odontoid  process. 
The  three  run  to  the  roughened  surface  at  the  antero- 
superior  part  of  the  body  of  the  atlas.  This  is  a  specimen 
of  an  axonoides  articulation ;  it  allows  motion  of  the  head 
from  side  to  side,  whereby  the  muzzle  may  be  made  to 
describe  a  circle. 

Vertebral  articulations. 

The  rest  of  the  vertebral  articulations  have  many 
characters  in  common.  The  anterior  convex  surface  of  the 
body  is  united  to  the  posterior  concavity  of  the  body  in 
front  of  it,  through  the  medium  of  an  intervertebral  disc  of 
cartilage,  which  is  soft  and  cartilaginous  centrally,  hard 
and  fibrous  externally.  Inferiorly  its  fibres  in  some  cases 
take  a  marked  direction  from  before  backwards  along  the 
central  line,  forming  the  inferior  vertebral  ligament,  most 
marked  in  the  lumbar  region,  where  it  affords  attachment 
to  the  crura  of  the  diaphragm.  The  superior  vertebral 
ligament  serves  to  strengthen  this  union  superiorly,  for  it 
runs  along  the  floor  of  the  spinal  canal,  its  whole  length 
consisting  of  a  series  of  bands  attached  to  the  roughened 
upper  surfaces  of  the  vertebral  centra,  widest  in  becoming 
attached  to  the  intervertebral  discs,  growing  narrow  oj^po- 
site  the  centres  of  the  vertebral  bodies,  in  forming  a  small 
band  passing  over  the  transverse  groove  for  a  venous 
sinus. 

The  anterior  oblique  processes  of  the  vertebrae  are 
united  to  the  posterior  oblique  processes  of  the  vertebrae 
in  front,  each  by  means  of  a  synovial  membrane  with  a 
strengthening  capsular  ligament.  This  articulation  is  ar^Aro- 
dial,  and  is  separated  inferiorly  by  the  intervertebral  gap 
from  the  amphiarthrodial  union  of  the  bodies,  supero-inter- 
nally  from  its  fellow  by  the  interlaminal  ligaments  which, 


104^  OUTLINES    OF    EQUINE    ANATOMY. 

running  from  the  posterior  margin  of  the  laminae  of  the 
anterior  vertebra,  gain  the  anterior  margin  of  the  laminae 
of  the  posterior  vertebra,  extending  inwards  as  far  as  the 
i7iter spinous  ligame7it,  which  runs  from  the  posterior  margin 
of  the  superior  spinous  process  of  one  vertebra  to  the 
anterior  margin  of  the  spine  of  the  next  bone.  This  is  not 
found  in  the  cervical  and  coccygeal  regions,  and  with  the 
interlaminal  becomes  converted  into  bone  in  the  sacral. 

The  sujiersjnnous  ligament  is  a  dense  band  of  white 
fibrous  tissue  extending  along  the  upper  extremities  of 
the  superior  spinous  processes  from  the  sixth  dorsal  to  the 
coccygeal  vertebra.  Posteriorly  it  becomes  gradually  lost. 
In  the  sacral  region  it  affords  attachment  to  the  important 
muscles  of  the  quarter,  triceps  abductor  femoris,  biceps 
rotator  tibialis,  and  ischio  tibialis  ;  and  in  extending  down- 
wards on  either  side  of  the  spinous  processes  forming  that 
flattened  band  which  becomes  attached  to  the  oblique 
processes  termed  the  sacral  ligament,  gives  attachment  to 
longissimus  dorsi  and  to  some  of  the  muscles  of  the  tail. 
It  is  very  intimately  blended  with  the  superior  ilio-sacral 
ligament  and  with  the  tendinous  layer  of  longissimus  dorsi 
against  the  posterior  spine  of  the  ilium.  In  front  of 
this  it  gives  attachment  laterally  to  longissimus  and  latis- 
simus  dorsi  and  to  other  muscles  through  the  medium  of 
the  lumbar  faschia.  In  the  cervical  region  it  is  repre- 
sented by 

Ligamentum  nuchse.  This  is  a  remarkable  body,  wholly 
composed  of  yellow  elastic  tissue,  situated  in  the  middle 
plane  of  the  neck,  consisting  of  three  portions,  super- 
spinous,  cordiform,  and  membraniform.  The  superspinous 
portion  consists  of  double  bands  extending  between  the 
superior  spinous  processes  of  the  cervical  and  four  an- 
terior dorsal  vertebrae ;  they  are  expanded  inferiorly, 
blending  with  the  interlaminal  ligaments.  Superiorly 
they  blend  with  the  memhraniform  portion  which  consists 
of  two  thin  layers  of  closely  and  somewhat  irregularly  in- 
terlaced elastic  fibres.  These  layers  rest  against  each 
other  by  their  inner  surfaces,  inferiorly  are  formed  by  a 
nuaiber  of  bands  running  upwards  and  backwards  from 
the  cervical  and  anterior  dorsal  spinous  processes.  Thus 
the  muscles  which  occupy  the  spaces  between  the  superior 
spinous  processes  in  this  region  lie  in  contact  with  their 
fellows  along  the  central  plane,  but  those  more  superiorly 


AETHROLOGY.  105 

placed  are  separated  by  tlie  two  layers  of  the  membranif orm 
portion  of  this  ligament.  The  muscles  mainly  thus  sei)a- 
rated  are  the  complexi  majores.  The  superior  margin  of 
this  portion  blends  with  the  cordiform  portion,  which  is  a 
rounded  band  of  yellow  elastic  tissue,  extending  from  the 
superior  extremity  of  the  spine  of  the  fifth  dorsal  ver- 
tebra (where  it  is  directly  continuous  with  the  superspinous 
ligament)  to  the  postero-inferior  part  of  the  crest  of  the 
occiput  and  the  line  between  its  scabrous  pits.  To  its 
upper  surface,  which  is  flattened,  is  attached  the  fatty  mane, 
and  on  either  side  it  affords  more  or  less  direct  attach- 
ment to  panniculus  carnosus,  levator  humeri,  splenius,  tra- 
pezius, rhomboideus  and  complexus  major.  This  elastic 
ligament  serves  to  support  the  head  without  muscular 
exertion. 

COSTAL  ARTICULATIONS. 

The  upper  extremity  of  the  rib  presents  three  synovial 
surfaces  for  union  with  the  spine.  The  tubercle  articu- 
lates with  the  transverse  process  of  the  vertebra  behind,  by  one 
facet  which  has  a  synovial  membrane  (strengthened  to  form 
a  capsular  ligament)  and  tivo  costo-transverse  lateral 
strengtheriincj  bands,  one  externally,  the  other  internally 
placed.  The  head  of  the  rib  presents  two  facets  separated 
by  a  roughened  groove.  The  facets  unite  by  diarthrosis 
with  corresponding  facets,  one  on  the  postero-superior  and 
lateral  part  of  the  body  of  the  vertebra  in  front,  the  other 
with  the  antero-superior  and  lateral  part  of  the  vertebra 
behind.  Each  of  these  facets  has  a  synovial  membrane 
strengthened  to  form  a  capsular  ligament,  and  from  the 
groove  between  ligamentum  teres  runs  to  the  intervertebral 
disc.  From  the  inner  surface  of  the  neck  of  the  rib  the 
stellate  ligament  runs,  and  divides  into  three  parts,  one  of 
which  runs  to  the  body  of  the  vertebra  in  front,  another  to 
the  body  of  the  vertebra  behind,  the  third  to  the  inter- 
vertebral disc  of  cartilage. 

The  gomphotic  union  of  the  inferior  extremity  of  the 
rib  with  the  sterno-costal  cartilage  is  maintained  by  con- 
tinuity of  the  costal  periosteum  with  the  investing  peri- 
chondrium of  the  cartilage.  The  inferior  extremity  of  the 
cartilage  of  elongatio7i  has  a  diarthrodial  union  with  the 
sternal  cartilage  or  bones  in  the  case  of  all  the  true  ribs  ; 
it  presents  a  synovial  membrane  and  tivo  lateral  ligaments, 


lOo  OUTLINES    OF   EQUINE   ANATOMY. 

the  superior  of  wliicli  blends  with  a  fibrous  hand  ivhicJi  runs 
from  one  extremity  of  the  sternum  to  the  other,  and  posteriorly 
is  continuous  with  the  ligament  by  which  the  inferior 
sharpened  extremities  of  the  false  ribs  are  connected 
together. 

ARTICULATIONS  OF  THE  FORE  EXTREMITY. 

Shoulder  or  scapulo-humeral  articulation 

is  the  union  of  the  glenoid  cavity  of  the  scapula  with 
the  head  of  the  humerus  ;  presents  only  a  capsular  ligament, 
directly  connecting  the  outer  circumferent  margins  of  these 
two  articular  surfaces.  It  is  lined  by  synovial  membrane. 
Anteriorly  its  external  surface  is  separated  by  fat  from 
the  tendon  of  flexor  brachii,  and  the  bursa  between  it  and 
the  antero-superior  part  of  the  humerus.  The  muscles  in 
contact  with  this  surface  are : — 

Internally — subscapularis  ;  posteriorly,  caput  magnum, 
scapulo-humeralis  posticus ;  externally,  scapulo-humeralis 
externus,  postea-spinatus,  and  antea  spinatus. 

This  is  a  good  example  of  a  rotatorial  joint. 

Elbow  or  brachio-humeral  articulation 

is  the  union  of  the  condyles  of  the  humerus  with  the 
articulatory  superior  surface  of  the  radius  and  that  of  the 
hamular  process  of  the  ulna.  This  articulation  has  a 
break  in  the  articular  cartilage  of  both  of  the  articular 
surfaces.  It  presents  a  capsular  ligament  and  two  lateral. 
The  outer  lateral  ligament  is  the  shortest  but  stoutest. 
It  runs  from  the  depression  on  the  external  surface  of  the 
outer  condyle  to  a  slight  prominence  at  the  superior  part 
of  the  outer  margin  of  the  radius.  The  inner  lateral 
ligament  superiorly  is  attached  to  a  depression  on  the 
inner  surface  of  the  inner  condyle,  runs  downwards,  is 
attached  to  a  prominence  at  the  superior  part  of  the  inner 
margin  of  the  radius,  passes  over  the  tendon  of  humeralis 
externus,  which  it  binds  down,  and  becomes  attached 
below  it. 

It  is  a  ginglymoid  articulation. 

Radio-ulnar  articulation 

has  been  necessarily  somewhat  minutely  described  in  our 
examination  of  its  component  bones. 


ARTHROLOGY.  107 

The  knee-joint,  carpus,  wrist  of  human  subject, 

consists  of  four  distinct  joints,   all  synovial  and  having 
distinct  capsular  ligaments.     The  radio-carpal  joint   is 
between  the  inferior  extremity  of  the  radius  and  the  sca- 
phoid, lunar,  and  cuneiform  bones  and  trapezium.  These  four 
bones  are  united  together  by  interosseous  and  connecting 
ligaments,  which  it  is  unnecessary  to  specify.     The  carpal 
joint  is  between  the  row  thus  formed,  and  the  lower  row 
formed  by    trapezoides,  magnum,  and  unciforme  united 
together  in  a  corresponding  manner,  which  by  their  under 
surfaces    come   into   connection    with   the  upper  surface 
of    the   metacarpus,  thus  forming  the    carpo-metacarpal 
joint.  The  last  joint  is  arthrodial;  the  two  former  ginglymoid; 
each  has  a  synovial  membrane,  which  in  every  case  dips 
down  between  the  small  facets  presented  by  their  small 
bones  for  union  with  one  another,  which  have  been  already 
minutely  described.     The  fourth  capsular  ligament  is  found 
surrounding   the  synovial  joint    which   trapezium  makes 
with  the  cuneiform  bone.     These  different  joints  are  con- 
nected by  lateral  ligaments  and  the  annular  ligaments.    The 
outer  lateral  ligament  may  be  divided  into  four,  the  inner 
into    three  parts.     The    annular  ligament    is    attached 
anteriorly  to  the  roughened  anterior  surfaces  of  all  the 
small  bones  of  the  knee,  also  to  the  roughened  supero- 
anterior   part  of   the  metacarpus.     It  anteriorhj  presents 
three  channels  running  from  above  downwards  with  special 
synovial  thecse  ;  the  inner  one  extends  obliquely  downwards 
to  the  inner  small  metacarpal  bone  and  gives  passage  to 
extensor  metacarpi  obliquus.     The  outer  one  runs  straight 
downwards  for  passage  of  extensor  pedis.     The  central  is 
broadest  and  terminates  opposite  the  supero- anterior  part 
of   metacarpi    magnum,    where    the    extensor  metacarpi 
magnus,  to  which  it  gives  passage,  is  attached.    A  continu- 
ation of  the  annular  ligament  surrounds  extensor  suffra- 
ginis  in  the  major  portion  of  its  course  from  the  elbow 
to  the  knee,   and  after  it  has   passed  through  a  sheath 
formed  by  the  outer  part  of  this  ligament,  from  which  it 
receives  a  reinforcing  land,  it  is  termed  ligamentum  exten- 
sorum.     On  the   surface  of  trapezium  it  forms  a  groove 
with  a  theca  for  the  lower  tendon    of   flexor  metacarpi 
externus.     The  arrangement  of  the  posterior  part  of  the 
annular  ligament    with  its  synovial  membranes,   and  its 


108  OUTLINES    OF   EQUINE    ANATOMY. 

superior  stisjjensory  and  suhcarpal  limiting  hands  lias  been 
ininutely  described  in  connection  with  the  tendons  of  the 
flexor es  pedis. 

Fetlock  joint 
is  the  union  of  the  inferior  extremity  of  the  cannon 
bone  superiorly  with  the  ossa  sesamoidea  and  os  suffra- 
ginis  inferiorly.  We,  therefore,  must  examine  how  the 
four  bones  are  united  together.  The  sesamoid  bones 
are  covered  posteriorly  by  fibro-cartilage,  for  they  form 
a  groove  over  which  the  flexor  tendons  play.  This  cartilage 
serves  to  connect  the  two  sesamoids  together  in  passing 
between  them,  forming  the  intersesamoid  ligament,  and 
superiorly  it  is  prolonged  above  the  bones,  continuous  with 
two  small  bands  of  a  decidedly  elastic  nature  running  to 
the  postero-inferior  part  of  the  large  metatarsal  bone.  The 
sesamoids  are  connected  to  os  suif  raginis  laterally  by  broad 
bands  of  white  fibrous  tissue,  lateral  sesamoid  ligaments^ 
inferiorly  by  several  ligaments,  the  inferior  sesamoideal. 

The  superficial  inferior  sesamoid  ligament  consists  of  two 
lateral  and  a  central  portion,  all  of  which  extends  from 
the  supero-posterior  part  of  os  suffraginis  to  the  inferior 
part  of  the  mass  formed  by  the  sesamoids  and  their  fibro- 
cartilage.  The  middle  ligament  has  a  widespread  triangular 
attachment  to  the  posterior  surface  of  os  suffraginis  and 
extends  to  the  inferior  part  of  the  sesamoid  mass.  The 
deep  ligament  rises  from  the  small  triangular  space  at  the 
supero-posterior  part  of  os  suffraginis,  sends  fibres  which 
cross  each  other  before  reaching  the  sesamoid  mass.  ,  The 
combined  sesamoid  and  sufFraginis  bones  are  attached  to 
the  large  metacarpal  bone  by  the 

Superior  sesamoideal  or  suspensory  ligament  which  ex- 
tends from  the  supero-posterior  part  of  os  metacarpi 
magnum  and  as  a  firm  fibrous  cord,  with  more  or  less 
numerous  muscular  fibres  interspersed,  inns  down  the 
back  of  the  limb  in  the  groove  formed  by  the  posterior 
surface  of  os  metacarpi  magnum  and  the  small  metacarpal 
bones  on  either  side.  Opposite  the  superior  part  of  the 
inferior  third  it  bifurcates,  one  division  running  to  the 
outer  part  of  each  sesamoid,  and  from  this  being  continued 
onwards  over  the  lateral  parts  of  os  suffraginis  to  blend 
with  extensor  pedis  on  the  anterior  part.  This  hgament 
corresponds  to  a  number  of  muscles  found  in  this  situ- 
ation   in   animals    which    have    five   digits  ;    sometimes 


ARTHROLOGY.  109 

these  miiscles  are  found  so  marked  in  the  horse  as  to  receive 
the  name  lumbrici.  The  lateral  ligaments  of  the  fetlock 
extend  from  the  infero-lateral  jmrt  of  metacarpi  magnum 
almost  as  high  up  as  the  inferior  bulbous  i^rominence  of 
the  splint  bone,  downwards  to  the  supero-lateral  part  of 
OS  suffraginis.  They  are  connected  together  by  the  capsular 
ligament,  a  thick  layer  of  white  fibrous  tissue  attached  to 
the  •  large  metacarpal  and  suffraginis  bones  close  to  their 
articulatory  surfaces  ;  internally  it  is  lined  by  the  synovial 
membrane  of  the  joint,  externally  in  contact  with  extensor 
pedis  tendon,  and  extensor  suffraginis.  The  annular  liga- 
ment passes  from  the  lateral  ligaments  behind  the  flexor 
tendons,  and  inferiorly  has  two  bands  which  blend  with 
perforatus  tendon  at  its  bifurcation. 

PASTERN  JOINT. 

The  inferior  articular  surface  of  os  suffraginis  is  main- 
tained in  apposition  with  the  superior  surface  of  os  coronse, 
anteriorly  by  the  tendon  of  extensor  pedis,  posteriorly  by 
the  long  inferior  sesamoideal  ligament.  On  each  side  is 
a  stout  lateral  ligament,  superiorly  extending  almost  half 
way  round  the  bone  from  underneath  extensor  pedis,  an- 
teriorly to  the  external  part  of  the  posterior  surface.  Its 
fibres  run  downwards  and  backwards,  and  after  covering 
the  inferior  attachment  of  flexor  pedis  perforatus  become 
attached  to  the  supero-lateral  parts  of  os  coronse,  some 
of  them  being  continued  on  to  form  one  of  the  divisions 
of  the  stellate  navicular  ligament,  others  joining  with 
similar  fibres  from  the  other  side  to  form  a  thin  fibrous 
layer,  the  superior  surface  of  which  intimately  blends  with 
the  perforans  tendon ;  the  inferior  gives  attachment  to  the 
fibrous  frog. 

The  coffin  or  pedal  joint  will  hereafter  be  described. 
(See  Foot.)     It  has  only  two  ligaments,  lateral. 

LIGAMENTS  OF  THE  PELVIS. 

The  superspinous  ligament  in  the  sacral  region  is  very 
thick  and  strong,  and  anteriorly  expands,  becoming 
attached  to  the  postero-superior  spinous  process  of  the 
ilium.  It  is  here  continuous  with  the  tendinous  structure 
of  longissimus  dorsi,  and  is  termed  the  superior  ilio-sacral 
ligament.  Becoming  attached  along  the  posterior  margin 
of  the  ilium,  extending  from  the  postero-superior  spinous 


110  OUTLINES    OF    EQUINE   ANATOMY. 

process  about  three  inches  downwards,  is  the  inferior  ilio- 
sacral  ligarnent,  the  fibres  of  which  run  obliquely  down- 
wards and  backwards,  to  become  attached  inferiorly  to  the 
transverse  ridge  of  the  sacrum,  and  to  become  continuous 
onwards,  blending  with  the  substance  of  the  sacrosciatic 
ligament,  after  forming  with  that  ligament  below  the  trans- 
verse ridge  a  canal  extending  from  before,  backwards, 
through  which  an  important  branch  of  the  gluteal  artery, 
with  its  accompanying  vein  and  nerve,  pass.  The  space  on 
the  lateral  part  of  the  sacinim  bounded  outwardly  by  the 
inferior  ilio-sacral  ligament  and  by  the  superior  part  of  the 
venter  ilii  is  occupied  by  the  posterior  part  of  longissimus 
dorsi,  and  when  this  is  removed,  a  continuation  of  the 
superior  spinous  ligament,  under  the  form  of  a  thick  layer 
of  fibres  running  downwards  and  backwards  over  the  lateral 
surface  of  the  sacral  spines,  is  exposed.  It  is  termed  the 
sacral  ligament. 

The  sacro-iliac  ligament  consists  of  a  number  of  stout 
ligamentous  fibres,  diverging  in  all  directions  from  the 
roughened  surface  around  the  auricular  facet  of  the  first 
sacral  transverse  process.  They  run  to  the  roughened 
surface  of  venter  ilii,  and  externally  blend  with  the  inferior 
ilio-sacral  ligament,  internally  being  continuous  with  a  stout 
ligamentous  band  running  towards  the  articulatory  margin 
on  the  anterior  part  of  the  last  lumbar  transverse  process, 
to  the  summit  of  which  also  a  few  scattered  fibres  run. 

The  sacro-sciatic  ligament  forms  the  postero -lateral 
boundary  of  the  pelvis.  Superiorly  it  is  attached  firmly 
along  the  whole  length  of  the  transverse  ridge  of  the 
sacrum,  inferiorly  it  becomes  attached  to  the  ischiatic  spine, 
and  to  the  tuberosity  of  the  ischium,  from  the  line  between 
these  two  prominences  becoming  reflected  inwards  as  a 
fibrous  layer  between  the  jpelvic  viscera,  and  the  internal  ohtu- 
rator  and  pyriformis  muscles  becoming  attached  to  the 
superior  edge  of  the  posterior  margin  of  the  ischium  and 
along  the  upper  part  of  the  inner  edge  of  the  os  innomi- 
natum.  Thus  between  the  ligament  and  the  bone  are  two 
spaces  ;  the  superior-ischiatic  notch  is  between  the  anterior 
margin  of  the  ligament  and  the  posterior  margin  of  the 
ilium,  and  gives  passage  to  the  gluteal  vessels  and  nerve 
and  the  sciatic  nerve.  The  inferior-ischiatic  notch  between 
the  neck  of  the  ischium  and  this  ligament,  where  it  is 
reflected  inwards,  gives  passage  to  the  obturator  internus 


ARTHROLOGY.  Ill 

and  pyriformis  tendons  ;  the  external  surface  of  this  liga- 
ment gives  attachment  to  some  of  the  large  muscles  of  the 
quarter  and  over  it,  almost  embedded  in  it,  runs  the  great 
sciatic  nerve.  Its  inner  surface  affords  attachment  to  re- 
tractor ani  and  compressor  coccygis.  The  obturator 
ligament  is  an  extremely  thin  layer  of  white  fibrous  tissue, 
with  difficnlty  demonstrable,  situated  between  the  internal 
and  external  obturator  muscles,  attached  to  the  margins  of 
the  foramen,  deficient  at  the  antero-external  part,  where 
the  obturator  vessels  and  nerve  gain  passage. 

ARTICULATIONS  OF  THE  HIND  EXTREMITY. 

Hip -joint 

is  formed  by  the  head  of  the  femur  and  the  acetabulum, 
maintained  in  apposition  by  ligaments.  The  acetabulum 
is  increased  in  depth  by  the  circumfere^itial  or  cotyloid 
ligament,  a  ring  of  fibro-cartilaginous  substance  attached 
around  its  margin,  it  passes  over  the  deficiency  on  the 
inner  side  of  the  cavity,  and  here  is  termed  the  trans- 
verse ligament;  thus  it  leaves  a  space  through  which  a 
dense  ligamentous  band  of  a  tendinous  nature  runs  to 
become  attached  to  the  break  in  the  articular  cartilage  on 
the  head  of  the  femur.  This  is  the  puhio -femoral  ligament, 
a  continuation  of  the  common  tendon  of  the  abdominal 
muscles  ;  it  runs  from  the  anterior  part  of  symphysis  pubis 
outwards  through  a  groove  on  the  under  surface  of  os 
pubis ;  some  of  the  muscular  fibres  of  rectus  abdominis 
are  directly  inserted  into  it ;  at  its  attachment  to  the 
head  of  the  femur  it  blends  with  ligamentum  tenses,  which 
passes  from  here  to  the  internal  roughened  part  of  the 
acetabulum.  From  the  free  margin  of  the  cotyloid  liga- 
ment the  capsular  ligament  extends  downwards,  to  become 
attached  around  the  outer  margin  of  the  articulatory 
surface  of  the  head  of  the  femur ;  it  is  lined  by  synovial 
membrane,  which  also  invests  the  pubio-femoral  and  teres 
ligaments. 

Stifle  joint 

corresponds  to  the  knee  of  the  human  subject ;  the  pa- 
tella, tibia,  fibula,  and  femur  assist  to  form  it.  Between 
the  condyles  of  the  femur  and  the  upper  articulatory 
surface  of  the  tibia  on  either  side  is  a  semilunar  disc  of 
fibro-cartilage.      These  are   convex  and  thick  externally 


112  OUTLINES    OF    EQUINE    ANATOMY. 

and  decrease  in  size  to  form  a  tliin  edge  at  tlie  internal 
margin  around  wliich  the  synovial  membrane  is  reflected 
from  the  upper  to  the  under  surface ;  to  the  outer 
margin  the  capsular  ligament  is  firmly  attached.  The 
anterior  extremity  of  each  cartilage  is  attached  by  a  liga- 
ment to  the  anterior  part  of  the  spine  on  the  upper  ex- 
tremity of  the  tibia.  The  posterior  extremity  of  each  by 
a  ligament  to  the  upper  extremity  of  the  tibia  behind  the 
spine,  but  the  outer  cartilage  in  addition  has  a  ligament 
extending  to  the  posterior  part  of  the  inter-condyloid 
fossa  of  the  femur.  The  femur  is  also  connected  to  the 
tibia  directly  by  the  crucial  and  the  lateral  ligaments. 
The  crucial  ligaments,  two  in  number,  can  only  be  exposed 
by  removal  of  one  of  the  condyles  of  the  femur.  One 
of  them  runs  from  the  anterior  part  of  the  groove  on  the 
tibial  spine,  to  become  attached  supero- posteriorly  to  the 
inner  surface  of  the  outer  condyle  in  the  intercondyloid 
fossa  ;  its  fibres  cross  at  right  angles,  the  other  crucial  liga- 
ment, which  runs  from  the  anterior  part  of  the  intercondy- 
loid fossa  downwards  and  backwards  to  the  superior  ex- 
tremity of  the  tibia  behind  the  spine. 

The  Older  lateral  ligament  is  superiorly  attached  to  the 
depression  on  the  outer  surface  of  the  outer  condyle  of  the 
femur  ;  it  crosses  the  tendon  of  popliteus  which  plays 
through  a  sheath  between  this  and  the  capsular  ligament, 
and  then  passes  on  to  the  femur.  This  ligament  becomes 
attached  below  to  the  upper  extremity  of  the  fibula ;  from  it 
peroneus  mainly  arises. 

The  inner  lateral  ligament  is  lomgeY  smd  narrower  than  the 
outer,  extending  from  the  internal  surface  of  the  inner 
condyle  downwards  to  the  supero-internal  j^art  of  the  tibia. 

The  patella  is  connected  to  the  femur  by  two  lateral 
ligaments.  The  inner  extremity  of  the  patella  is  continued 
as  a  piece  of  fibro-cartilage  which  plays  over  the  inner 
condyle,  and  from  this  the  inner  ligament  runs  to  the  inner 
surface  of  the  internal  femoral  ridge.  It  is  smaller  than 
the  outer,  which  runs  from  the  outer  extremity  of  the 
patella  to  the  corresponding  part  of  the  outer  ridge. 

The  patella  is  connected  to  the  tibia  by  three  straight 
ligaments.  The  inner  runs  from  the  complementary  car- 
tilage on  the  inner  side  of  the  patella  to  the  supero-internal 
angle  of  the  ridge  on  the  antero- superior  part  of  the  tibia. 
The  outer,  which  is  composed  of  two  portions,  extends  from 


AETHROLOGY.  1  ]  3 

the  outer  extremity  of  tlie  patella  to  the  supero-external 
angle  of  the  same  ridge.  The  capsular  ligament,  after  con- 
necting together  the  two  articulatory  surfaces  posteriorly 
and  laterally,  and  internally  becoming  attached  to  the 
semilunar  cartilages,  externally  to  the  lateral  ligaments 
(partially  separated  from  the  outer  by  the  tendon  of  pop- 
liteus),  blends  with  the  inner  and  the  outer  straight 
ligaments  of  the  patella,  connecting  them  together,  and 
covering  the  central  straigJit  ligament,  which  commences 
about  the  centre  of  the  anterior  surface  of  the  patella, 
plays  over  a  bursa  on  that  bone,  is  separated  from  the  main 
joint  by  a  quantity  of  fat,  plays  over  another  bursa  at  the 
central  part  of  the  superior  extremity  of  the  tibial  ridge, 
and  becomes  attached  below  it. 

The  synovial  membranes  of  this  joint  are  two  or  three  in 
number,  for  in  some  cases  we  see  the  cavity  of  the  joint 
between  the  femur  and  the  patella  communicating  with  that 
of  the  inner  condyle  of  the  femur.  The  cavity  of  the  outer 
condyle  always  remains  distinct.  These  cavities  frequently 
communicate  with  the  important  bursae  in  the  neighbour- 
hood. The  condyles  come  directly  into  contact  with  the  la- 
teral parts  of  the  spine  of  the  tibia,  the  upper  surfaces  of  the 
semilunar  cartilages  are  concave  1o  accommodate  the  con- 
vex surfaces  of  the  condyles,  their  under  surfaces  are  plane. 

The  mode  of  union  of  the  fibula  to  the  tibia  has  been 
already  described. 

HOCK  JOINT. 

The  small  bones  of  the  hock,  like  those  of  the 
knee,  are  united  together  by  interosseous  and  connectincj 
ligaments,  thus  producing  two  rows,  the  superior  formed 
by  astragalus  and  calcis,  the  inferior  by  the  cuboid 
and  three  cuneiform  bones.  These,  together  with  the 
metatarsus,  form  the  tarsal  and  tar  so -metatarsal  gliding 
joints,  lubricated  with  synovia  secreted  by  membranes, 
which  extend  to  the  facets  situated  between  the  several 
small  bones  ;  generally  a  distinct  synovial  sac  may  be  dis- 
tinguished between  the  component  bony  layers  of  the 
lower  row. 

The  true  hock-joint  is  the  ginglymoid  articulation  formed 
by  the  apposition  of  the  inferior  grooves  of  the  tibia  with 
the  superior  ridges  of  astragalus.  This  joint  presents  a 
capsular  ligament,  attached  around  the  edge  of  the  articu- 

8 


114  OUTLINES    OF   EQUINE   ANATOMY. 

latory  surfaces,  which  at  the  postero-internal  part  is 
thickened  and  fibro-cartilaginous,  its  external  surface  being 
here  concave  and  lubricated  with  synovia,  forming  part 
of  that  theca  in  which  the  perforans  tendon  glides. 

The  lateral  ligaments  of  the  JiocTc  are  two  in  number,  and 
extend  from  the  malleoli  of  the  tibia  to  the  supero- lateral 
l^arts  of  the  large  and  respective  small  metatarsal  bones  ; 
the  outer  is  the  largest.  Both  of  them  may  be  divided  into 
several  parts. 

The  posterior  annular  ligament  is  thickened  in  covering 
the  bones  on  the  postero-internal  part  of  the  joint  in  the 
groove,  in  which  the  perforans  tendon  plays  ;  it  likewise 
becomes  reflected  from  the  posterior  border  of  os  calcis  to 
blend  with  the  posterior  margin  of  the  inner  lateral  liga- 
ment, binding  down  the  perforans  tendon  and  continued  on 
to  retain  the  tendon  of  flexor  pedis  accessorius  in  its  groove 
behind  the  internal  malleolus. 

The  anterior  annular  ligament  becomes  marked  as  three 
hands.  The  superior  extends  across  the  antero-inferior  part 
of  the  tibia,  over  the  flat  surf  ace,  binding  down  the  tendons 
of  flexor  metatarsi  and  extensor  pedis,  inclined  obliquely 
from  within  outwards  and  downwards,  and  continued  on  to 
retain  the  tendon  of  peroneus  in  its  groove  on  the  outer 
malleolus  of  the  tibia.  The  middle  hand,  extending  from 
the  cuboid,  winds  round  extensor  pedis  tendon,  and  then 
blends  with  that  division  of  the  flexor  metatarsi  tendon 
which  passes  to  the  same  bone.  The  inferior  hand,  closely 
connected  in  the  fresh  subject  with  the  middle,  runs  from 
the  superior  extremity  of  the  outer  small  metatarsal  bone 
over  extensor  pedis  tendon  to  the  central  line  of  the  supero- 
anterior  part  of  the  large  metatarsal  bone. 

The  calcaneo-euboid  ligament  extends  from  the  posterior 
border  of  os  calcis  along  its  whole  length  downwards  to  the 
superior  part  of  the  outer  small  metatarsal  bone.  Exter- 
nally it  blends  with  the  external  lateral  ligament,  internally 
with  the  posterior  annular  ligament.  A  large  and  impor- 
tant synovial  membrane  covers  the  inner  surface  of  the 
capsular  ligament. 

None  of  the  other  ligaments  of  the  hock  require  special 
notification. 

The  other  articulations  of  the  hind  limb  resemble 
those  of  the  fore  limb,  to  the  description  of  which  reference 
may  be  made  when  the  dissection  arrives  at  this  stage. 


SPECIAL   ANATOMY.  115 


PART  lY.— SPECIAL  ANATOMY. 
The  Head. 

From  the  angle  formed  at  the  meeting  of  the  incisions 
through  the  skin  downwards  from  the  ear,  and  backwards 
from  the  lower  lip,  the  operator  commences  to  remove  the 
skin  in  the  antero-superior  direction  as  far  as  the  root  of 
the  ear,  the  eyelids,  and  the  central  line  of  the  face  ;  this 
done  he  works  forward  towards  the  lips  and  the  nostril, 
where  the  muscular  fibres  are  found  closely  in  contact  with 
the  skin,  in  some  places  being  inserted  into  it.  The  roots 
of  some  of  the  long  hairs  which  form  the  "  feelers  "  will  be 
also  cut  through  in  removing  the  skin  from  the  lips.  From 
the  zygomatic  ridge  to  the  centre  of  the  submaxillary 
space  the  panniculus  in  a  thin  layer  lies  immediately  in 
contact  with  the  skin,  and  through  it  may  be  seen  the 
branches  of  the  facial  nerve,  and  the  masseter  externus 
muscle.  Its  fibres  converge  from  here  towards  the  angle 
of  the  mouth,  where  they  blend  with  other  muscles,  especi- 
ally orbicularis  oris,  forming  the  muscular  band  termed 
retractor  anguli  oris. 

To  the  same  point,  and  to  the  upper  lip  above  it,  run 
fibres  forming  a  thin  layer  extending  from  the  zygomatic 
ridge,  and  some  from  the  muscles  of  the  lower  eyelid.  This 
is  zygomaticus,  which  muscle  forms  the  central  part  of  the 
superficial  subcutaneous  layer  of  the  face. 

The  upper  part  of  this  layer  is  formed  by  levator  labii 
superioris  alseque  nasi,  which  is  attached  superiorly  to  the 
nasal,  frontal,  and  lachrymal  bones  at  their  point  of 
junction,  and  runs  downwards  and  forwards  to  be  inserted 
into  the  point  of  the  false  nostril,  the  wing  of  the  nostil, 
and  the  upper  lip,  blending  with  the  other  muscles  of  this 
part. 

The  fibres  of  this  muscle  are  separated  inferiorly  into  two 


116  OUTLINES    OF    EQUINE    ANATOMY. 

portions  by  the  passage  of  the  insertion  portion  of  retractor 
labii  superioris,  which  spread  out  in  their  course  towards 
the  ala  of  the  nostril  and  the  upper  lip,  while  their  origin 
from  the  superior  maxillary  bone  in  front  of  the  termina- 
tion of  the  zygomatic  ridge  is  hidden  by  zygomaticus. 

Extending  round  the  free  margin  of  the  lips  are  a  number 
of  fibres  of  red  muscular  substance  into  which  all  the  mus- 
cles running  to  these  organs  seem  to  pass ;  this  is  orbicu- 
laris oris,  the  muscle  by  which  the  lips  are  closed  and  the 
animal  enabled  to  grasp  small  articles  (as  oat  grains)  on  a 
flat  surface.  This  muscle  is  nowhere  intimately  attached 
to  the  bone,  but  is  composed  of  a  series  of  short  fibres 
encircling  the  oral  opening. 

The  frontal  and  nasal  bones  are  immediately  in  contact 
with  the  skin  on  the  forehead  and  nose,  but  about  opposite 
to  the  nasal  peak  the  tendon  of  nasalis  longus  labii 
superioris  emerges  from  beneath  lev.  labii  sup.  alseque 
nasi,  and  running  over  the  cartilaginous  prolongation  of 
the  nasal  bones,  where  it  is  lubricated  with  synovia,  it  gains 
the  anterior  surface  of  the  alse  of  the  nostril,  which  are 
here  to  be  seen  covered  by  dilator  naris  anterior  (which 
runs  from  the  external  surface  of  one  ala  to  that  of  the 
other)  ;  here  the  tendon  blends  with  the  corresponding 
tendon  from  the  other  side  of  the  face,  and  from  the  point 
of  union  the  fibres  radiate  to  blend  with  orbicular  oris,  and 
become  inserted  into  the  skin  of  the  upper  lip. 

The  false  nostril  fills  the  angle  formed  between  this 
tendon  and  the  levator  labii  sup.  alseque  nasi.  From  the 
anterior  edge  of  the  nasal  bones,  extending  as  far  back  as 
where  this  bone  meets  the  anterior  maxillary  bone,  the 
dilator  naris  superior  arises,  and  runs  to  be  inserted  into 
the  false  nostril  along  its  whole  superior  margin. 

Below  retractor  anguli  oris  the  terminal  portion  of 
retractor  labii  inferioris  with  a  small  round  tendon  is 
found  going  to  blend  with  orbicularis  oris  in  the  lower  lip 
(this  tendon  is  connected  to  the  inferior  maxillary  bone 
below  the  corner  incisor  by  a  distinct  band  of  muscular 
fibres  in  some  subjects),  and  below  this  the  bone  is  sub- 
cutaneous. 

On  removal  of  the  superficial  muscular  layer  of  the  face 
we  expose  the  masseter  externus,  a  huge  square  mass  of 
muscle  arising  along  the  whole  length  of  the  under  surface 
of  the  zygomatic  process,  and  passing  to  the  whole  external 


SPECIAL    ANATOMY.  ]17 

surface  of  the  branch  of  the  inferior  maxilla.  At  its  origin 
it  is  tendinous,  and  through  its  substance  run  strong  tendi- 
nous bands,  which  are  inserted  below  into  irregular  ridges  ; 
these  bands  are  a  provision  for  the  constant  closure  of  the 
jaws  when  not  required  to  be  separated  in  mastication  or 
otherwise,  for  this  muscle,  with  temporalis,  pterygoideus, 
and  masseter  internus  serve  to  close  the  month.  In  many 
other- situations  we  shall  observe  tendinous  bands  running 
throughout  the  whole  length  of  auiscles  to  support  weight, 
without  the  active  contraction  of  muscular  fibre  which 
would  weary. 

Along  the  posterior  part  of  the  superior  margin  of  mas- 
seter externus  we  see  the  temporal  artery  with  an 
accompanying  vein,  which  vein  is  sujDeriorly  placed.  This 
artery  is  one  of  the  three  terminal  trunks  of  the  external 
carotid,  and  after  winding  round  the  angle  of  the  jaw 
posteriorly,  proceeds  for  about  two  inches  on  the  external 
surface  of  this  muscle,  and  then  dips  down  into  its  sub- 
stance ;  the  pulse  is  frequently  taken  at  this  artery.  Along 
the  anterior  margin  of  the  masseter  externus  run  the 
submaxillary  artery  and  vein,  with  the  duct  of  the  parotid 
salivary  gland.  The  artery  is  almost  invariably  the  most 
anteriorly  situated,  but  the  position  of  the  vein  and  duct  is 
not  constant.  At  first  in  contact  with  the  inferior  maxillary 
bone  they  next  pass  over  retractor  labii  inf erioris,  when  the 
artery  gives  off  a  branch  running  forwards,  the  inferior 
labial  and  several  branches,  the  anterior  masseteric,  which 
run  from  it  posteriorly  to  the  masseter  muscle.  They  then 
run  on  to  buccinator  and  caninus,  the  muscles  which  form 
the  cheek  ;  about  the  centre  of  this  muscular  mass  the  duct 
dips  between  the  muscular  fibres,  and  having  proceeded  a 
short  distance  beneath  the  buccal  mucous  membrane,  opens 
into  the  mouth  at  a  small  eminence  or  papilla  situated 
opposite  the  space  between  the  second  and  third  molar 
teeth  (but  the  position  of  this  opening  is  not  constant).  At 
the  anterior  extremity  of  the  zygomatic  spine  the  sub- 
maxillary artery  divides  into  the  superior  labial  and  facial. 
This  division  occurs  just  after  the  vessel  has  passed  over 
the  originating  tendon  of  retractor  labii  superioris ;  the 
superior  labial  branch  runs  forward,  being  mingled  with 
the  fibres  of  the  superior  maxillary  division  of  the  fifth 
cranial  nerve,  which  here  emerge  from  the  infra-orbital 
foramen,  and  run  to  the  upper  lip.     With  these  it  pierces 


lis  OUTLINES    OF    EQUINE    ANATOMY. 

the  lip,  and  so  gains  tlie  incisive  foramen,  where  it  combines 
with  the  corresponding  artery  from  the  opposite  side,  and 
the  trunk  thus  formed  joins  with  the  arch  formed  by  the 
union  of  the  two  palatine  arteries,  which  run  along  the 
sides  of  the  roof  of  the  mouth.  The  facial  artery  runs 
upwards,  anastomosing  with  branches  of  the  ocular  arteries, 
which  bend  round  the  margin  of  the  orbit.  At  its  upper 
part  it  passes  over  the  origin  of  nasalis  longns  labii 
superioris  (which  arises  from  about  the  point  of  junction 
of  the  nasal,  malar,  and  lachrymal  bones). 

By  removal  of  zygomaticus  and  retractor  anguli  oris  we 
expose  buccinator  and  caninus.  These  two  muscles  are 
intimately  blended ;  buccinator  anteriorly  blends  with 
orbicularis  oris,  its  fibres  run  directly  backwards  to  become 
inserted  into  the  anterior  margin  of  the  ramus  of  the  lower 
jaw,  posteriorly  to  the  alveolar  cavities  ;  it  is  also  attached 
slightly  to  the  alveolar  ridges  and  to  the  tuberosity  of  the 
superior  maxilla.  To  show  this  an  incision  must  be  made 
through  masseter  externus,  whereby  it  will  be  found  to 
cover  superiorly  a  varicose  vein  situated  immediately 
beneath  the  zygomatic  spine,  running  from  the  submaxil- 
lary vein  on  the  cheek  through  the  foi-amen  lacerum  orbi- 
tale  to  the  cavernous  sinus  ;  below  this  is  one  of  the  buccal 
salivary  glands  from  two  to  three  inches  in  length,  similar 
in  structure  to  the  parotid  gland,  the  secretion  of  which  is 
poured  into  the  mouth  through  numerous  foramina  opening 
upon  a  line  of  papillary  eminences  of  the  buccal  mucous  mem- 
brane, opposite  to  the  upper  molar  teeth.  Below  this  gland 
is  seen  buccinator  intimately  blended  with  retractor  labii 
inferioris,  inserted  as  above  mentioned.  Caninus  is  com- 
posed of  two  distinct  layers  of  arched  fibres,  which  arise 
from  the  superior  and  inferior  maxillary  bones  respectively 
at  the  interdental  spaces,  run  towards  the  central  line  of 
the  anterior  part  of  buccinator,  where  they  blend  together 
and  with  that  muscle,  sending  some  straight  fibres  to  blend 
with  it  posteriorly.  By  raising  the  infero-anterior  part  of 
buccinator,  just  in  front  of  masseter  externus,  we  expose 
the  inferior  buccal  glands,  in  every  respect,  except  situa- 
tion, resembling  the  superior ;  they  lie  in  immediate  con- 
tact with  the  buccal  mucous  membrane,  with  which  the 
internal  surface  of  buccinator  is  intimately  attached 
throughout  the  rest  of  the  cheek.  Passing  around  the 
anterior  margin  of  the  coracoid  process  of  the  inferior  max- 


SPECIAL   ANATOMY.  119 

illary  bone  is  the  buccal  hrancJi  of  the  inferior  maxillarij 
division  of  the  fifth  cranial  nerve;  it  sends  some  large  fibres 
to  the  buccal  glands,  and  runs  onwards  to  supply  buc- 
cinator and  caninus  as  far  forwards  as  the  angle  of  the 
mouth.  The  facial  hranch  of  the  same  nerve  winds  round 
the  posterior  margin  of  the  lower  jaw  just  below  the  con- 
dyle, combines  with  the  seventh  nerve  or  portio  dura,  and 
proceeds  over  the  cheek  on  the  external  surface  of  masseter 
externus.  One  of  its  portions  runs  with  the  temporal 
artery,  the  inferior  branch  passes  to  the  lower  lip,  and 
there  unites  with  that  portion  of  the  dental  branch  of  the 
inferior  maxillary  nerve,  which  passes  out  of  foramen 
nienti  (or  the  anterior  maxillary  foramen).  The  middle 
and  largest  branch  proceeds  over  the  cheek,  and  sends 
communicating  fibres  to  the  nerve  which  passes  out  of  the 
infra-orbital  foramen;  these  pass  in  a  curved  manner 
around  the  origin  of  retractor  labii  superioris,  but  the 
greater  number  of  the  fibres  blend  with  the  infra-orbital 
fibres,  and  run  to  the  nostril  and  upper  lip.  Some  small 
muscles  on  the  muzzle  remain  yet  to  be  noticed. 

Dilator  naris  inferior  arises  from  the  superior  process 
of  the  anterior  maxillary  bone,  winds  round  its  smooth 
superior  margin,  and  becomes  inserted  into  the  cartilagi- 
nous anterior  extremity  of  the  inferior  turbinated  bone 
into  the  skin  of  the  false  nostril.  From  the  superior  ex- 
tremity of  the  false  nostril  a  small  muscle  running  to  the 
superior  maxillary  hone  just  above  the  termination  of  the 
zygomatic  ridge  may  frequently  he  found. 

Depressor  labii  superioris  arises  from  the  external  sur- 
face of  the  body  of  the  anterior  maxilla  around  the  alveolae 
of  the  incisors,  and  extending  back  to  the  canines :  it 
becomes  inserted  into  the  mucous  membrane  lining  the 
upper  lip,  and  may  be  exposed  by  removing  this  mem- 
brane and  the  labial  glands.  It  will  be  found  to  blend 
centrally  with  its  fellow.  In  the  lower  lip  we  find  a 
corresponding  muscle,  levator  labii  inferioris.  Internally 
to  these  muscles  is  a  layer  of  salivary  glandular  substance 
from  which  run  numerous  ducts  which  pierce  the  mucous 
membrane  of  the  lips,  by  inversion  of  which  their  openings 
may  be  rendered  visible  to  the  naked  eye.  The  structure 
of  the  lower  lip  is  completed  by  a  mass  of  fatty  matter 
throughout  which  many  muscular  fibres  are  interspersed. 
The  lips,  therefore,  consistof  skin,  muscle,  glandular  struc- 


12Q  OUTLINES    OF    EQUINE    ANATOMY. 

ture,  and  mucous  membrane,  witli  veins,  arteries,  lymph- 
atics, and  especially  nerves,  the  large  size  of  which  renders 
the  "  twitch  "  such  an  effectual  "  sedative  ?"  It  is  orbi- 
cularis oris  which  forms  the  greater  part  of  the  lij^s,  and 
which  brings  the  two  lips  into  close  connection  at  their 
extremities,  whereby  the  commissures,  or  angles  of  the  mouth, 
are  formed.  The  lips  are  the  organs  of  prehension  of  the 
horse,  and  present  an  external  surface  from  which  long 
hairs,  ''feelers,''  project,  more  especially  from  the  inferior 
central  prominent  portion  commonly  called  the  chin.  The 
internal  surface  of  the  lips  is  concave,  moulded  upon  the 
anterior  surfaces  of  the  inferior  and  anterior  maxillary 
bones  (which  is  covered  by  the  dense  mucous  membrane 
which  forms  the  gum)  and  upon  the  anterior  surfaces  of 
the  crowns  of  the  incisors.  The  free  margins  of  the  lips 
are  in  contact  with  each  other,  or  sej^arated  according  as 
the  mouth  is  shut  or  open. 

The  remainder  of  the  skin  may  now  be  removed,  when 
another  orbicularis  muscle  will  be  exposed  in  the  eyelids, 
which  it  tends  to  approximate  and  to  maintain  in  appo- 
sition. This  is  orbicularis  palpebrarum,  which  is  attached 
by  a  small  tendon  to  the  lachrymal  tubercle  situated  on 
the  facial  surface  of  the  lachrymal  bone.  Its  fibres  extend 
into  the  upper  and  the  lower  lids,  and  meet  at  the  o^der 
angle,  commissure,  or  canthus  of  the  eye.  It  is  exter- 
nally in  contact  with  the  skin,  which  is  thin  and  smooth 
in  this  neighbourhood.  Internally  it  is  fixed  to  the  bones 
which  form  the  rim  of  the  orbit  by  loose  areolar  tissue, 
and  in  the  substance  of  the  upper  eyelid  is  attached  to 
the  tarsal  cartilage  or  ligament,  a  small  semilunar  portion 
of  yellow  elastic  cartilage  which  is  thickest  in  the  centre, 
and  grows  narrower  and  thinner  until  it  terminates  in  a 
point  at  either  extremity  in  becoming  continuous  with  the 
white  fibrous  tissue  of  the  eyelid.  It  is  sometimes  found 
in  the  lower  lid,  but  is  then  mostly  fibrous.  On  the 
internal  SLirface  of  this  cartilage,  and  running  in  small 
parallel  lines  visible  through  the  mucous  membrane  lining 
the  eyelid,  in  a  direction  perpendicular  to  its  free  margin, 
are  the  meibomian  glands,  specially  modified  sebaceous 
glands,  the  product  of  which  serves  to  prevent  overflow 
of  tears  on  to  the  external  surface  of  the  lids.  To  orbi- 
cularis palpebrarum  run  several  muscles. 

Levator  palpebrae  superioris  externus  runs   from  the 


SPECIAL    ANATOMY. 


121 


root  of  the  orbital  process  of  the  frontal  bone  to  the  npper 
eyelid,  where  it  blends  with  orbicularis,  from  the  lower 
part  of  which  muscle  levator  labii  superioris  alseque  nasi 
and  zjgomaticus  in  part  take  their  origin.  The  eyelids, 
therefore,  are  two  semilunar  folds  which  are  adapted  to 
cover  the  anterior  surface  of  the  eyeball.  They  are  com- 
posed externally  of  skin,  internally  of  mucous  membrane, 
nam-ed  the  conjunctiva,  which  becomes  reflected  over  the 
tunica  albuginea  and  the  cornea,  thus  covering  all  that 
portion  of  the  eye  which  is  naturally  visible,  and  serving 
to  retain  the  eyeball  in  its  proper  relation  with  the  palpe- 
bral fissure,  by  its  smooth  surface  to  facilitate  the  move- 
ments of  the  eyelids,  and  to  protect  the  eye.  That  portion 
of  it  which  lines  the  eyelids  and  covers  the  tunica  albu- 
ginea is  vascular,  but  its  continuation  ovei'  the  cornea  is 
simjjly  a  basement  membrane,  with  a  single  layer  of  tesse- 
lated  epithelial  cells,  which  is  transparent  and  thus  causes 
no  obstruction  to  vision.  Between  these  two  layers  of  the 
eyelid  are  situated  muscular  structure,  vessels,  nerves,  the 
meibomian  glands  and  the  tarsal  ligament.  ^  The  free 
borders  of  the  eyelids  are  broad  and  only  come  into  appo- 
sition by  their  outer  edges  when  the  lids  meet ;  thus  a  trian- 
gular canal  is  formed  by  which  the  tears  are  directed 
towards  the  inner  angle  of  the  palpehral  fissure,  the  space 
between  the  eyelids.  Along  the  outer  edge  of  this  margin 
we  see  the  eyelashes,  cilise  ;  long  curved  hairs,  those  of 
the  upper  lid,  the  strongest  and  longest,  run  in  an  upward 
direction,  those  of  the  lower  lid  downwards.  This  margin 
also  presents  in  each  eyelid  a  row  of  openings  of  the 
meibomian  glands,  and  at  the  inner  extremity  a  much  larger 
opening  ;  these  latter  are  the  puncta  lachrymalia,  through 
which  the  tears  pass  on  their  way  from  the  front  of  the 
eye  to  the  nasal  chamber.  The  points  at  which  the  eye- 
lids meet  are  termed  the  cantM  ;  the  outer  or  temporal 
cantlius  is  in  the  form  of  an  acute  angle,  and  here  the 
eyelids  are  in  direct  contact  with  the  eyeball ;  the  inner 
or  nasal  canthus  presents  a  rounded  diverticulum  in  which 
is  situated  a  small  rounded  nodular  body  covered  by  a 
very  thin  dark  skin  which  presents  a  few  short  and  fine 
hairs.  This  is  the  canincula  lachrymalis,  which  is  merely 
a  mass  of  connective  tissue  and  vessels,  and  is  situated 
between  the  puncta  lachrymalia  into  which  it  serves  to 
direct  the  tears.     Before  departing  from  consideration  of 


122  OUTLINES    OF    EQUINE    ANATOMY. 

the  eyelids  we  may  notice  that  into  the  inner  surface  of 
the  tarsal  ligament  is  inserted  by  a  broad  tendon  the 

Levator  palpebrse  superioris  internus,  a  muscle  which 
arises  from  the  upper  part  of  the  orbital  hiatus  above 
rectus  superior,  and  passes  within  the  periorbital  membrane 
to  become  inserted  as  described.  By  playing  over  the  eye- 
ball it  is  enabled  to  raise  the  eyelid. 

The  eyelids  receive  blood  from  the  ophthalmic  artery, 
from  the  facial  artery,  and  from  the  ocular  and  supra- 
orbital branches  of  the  internal  maxillary  artery.  Their 
nerves  are  derived  from  the  ophthalmic  division  of  the 
fifth  cranial  nerve,  the  supra-orbital  branch  of  which  is 
remarkable  as  passing  to  the  foramen  of  that  name  from 
the  foramen  lacerum  orbitale  externally  to  the  periorbital. 

On  the  supero-posterior  part  of  the  head,  on  either  side 
of  the  poll,  are  situated  the  structures  which  compose 
the  external  ear.  These  consist  of  three  cartilages  on  each 
side,  of  the  muscles  which  act  upon  them,  and  of  the  skin 
which  covers  one  of  them  extending  inwards  to  line  the 
external  ear.  Situated  nearest  to  the  orbit,  resting  on  the 
rounded  mass  which  is  named  the  temporal  muscle,  is  an  irre- 
gularly triangular  shaped  cartilage,  which  seems  to  be  con- 
nected to  the  other  cartilages  by  muscle  alone  :  this  is  the 
scutiform  cartilag'e.  From  its  external  surface  the  external 
scuto- auricular es  muscles  run  to  theconchial  cartilage,  and 
similar  muscles  may  be  found  attached  to  its  internal  sur- 
face. The  conchial  cartilage  is  a  portion  of  membraniform 
cartilage  twisted  upon  itself  in  such  a  manner  as  superiorly 
to  present  a  sharp  point,  externally  a  wide  broad  slit, 
infero-posteriorly  a  cup-shaped  diverticulum,  infero- 
anteriorly  a  tubular  portion  along  one  side  of  which  we 
see  an  irregular  slit  running  outwards,  filled  with  fibrous 
tissue  (and  from  the  other  side  a  thin  process  runs 
to  be  attached  below  to  the  guttural  pouch),  which 
is  connected  to  the  external  auditory  process  by  a  ring- 
shaped  piece  of  cartilage,  the  annular  cartilage.  This 
cartilage  is  connected  to  the  external  auditory  process  by 
yellow  elastic  tissue,  and  similarly  to  the  conchial  cartilage  ; 
the  circular  portion  of  the  conchial  will  fit  on  the  annular, 
and  the  annular  on  the  bony  process  like  the  joints  of  a  tele- 
scope, but  this  action  is  regulated  by  muscles  which  run 
from  one  cartilage  to  the  other,  which  with  those  running 
from    the    scutiform    cartilage   constitute    the    intrinsic 


SPECIAL   ANATOMY.  123 

muscles  of  the  external  ear.     To   the  conchial  cartilage 
run  the   extrinsic    auricular  muscles ;    those    anteriorly 
situated  are  the  attrahentes,  and  are  attached  to  the  zygo- 
matic process  and  to  the  parietal  ridges.     The  retrahentes 
are  attached    to  the  liganientum  nuchse,  and  by  areolar 
tissue   to  the  muscles  situated  externally  to  the  muscles 
of  the  poll.     The  adductor  muscles  run  from  the  crest  of 
the    occiput  ;    debility    of   these  causes    the   animal    to 
become  "  lop-eared."  Parotideo  auricularis  is  the  abductor ; 
it  runs  from  the  external  part  of  the  base  of  the  conchial 
cartilage,  to  become  attached  below  to  the  external  surface 
of  the  parotid  gland.     It  is  not  directly  subcutaneous,  but 
covered  by  a  thin  layer  of  panniculus.    Around  the  base 
of  the  conchial  cartilage  is  a  quantity  of  fat,  which  facili- 
tates its   movements.     The  common  integument  covering 
the  external  surface  of  this  cartilage  at  its  upper  third  is 
reflected  over  its  margin  at  the  meatus  auditorius  exter- 
nus  (or  slit)  to  line  the  conchial  and  annular  cartilages, 
and  the  external  auditory  canal,  at  the  bottom  of  which  it 
covers  the  external  surf  ace  of  membrana  tympani.     It  is 
very    fine   and   at  the    internal   surface   of    the  conchial 
cartilage    presents     long   hairs    which   seem    to    close    up 
the  external  opening ;  they  serve  to  prevent  the  ingress  of 
foreign   matters.     More   internally    it  presents  sebaceous 
glands  modified  for  the  production  of  the  cerumen  or  wax 
of  the  ear,  ceruminous  glands.    We  notice  that  the  external 
ear  of  the  ass  is  more  developed  than  that  of  the  horse. 
The  external  ear  receives  blood  by  the  anterior  and  pos- 
terior auricular  branches  of  the  external  carotid  artery ; 
the  latter  sends  a  large  branch,  middle  auricular,  to  the  in- 
ternal surface  of  the  conchial  cartilage.     The  nerves  of  the 
external  ear  are  derived  from  the  facial,  fifth  cranial,  and  first 
cervical  nerves. 

The  inferior  maxilla  must  now  be  partially  removed 
by  incision  through  the  interdental  space  and  through  its 
neck  after  masseter  externus  has  been  separated  from  its 
inferior  attachment,  and  thrown  upwards  over  the  zygo- 
matic spine.  By  removing  the  piece  of  bone  thus  separated 
we  expose  the  anterior  attachment  of  digastricus  inf eriorly, 
and  above  tbis  we  cut  through  the  attachment  of 

Mylo-hyoideus,  which  arises  from  the  alveolar  ridge  at 
the  superior  part  of  the  internal  surface  of  the  inferior 
maxilla.     Its  fibres  run  towards  the  centre  of  the  inter- 


12-i  OUTLINES    OF    EQUINE    ANATOMY. 

maxillary  space,  where  they  blend  witli  tliose  of  its  fellow, 
thus  forming  a  sling  for  the  tongue  and  a  central  raphe, 
which  posteriorly  is  attached  to  the  inferior  margin  of  the 
spur  process  of  os  hyoides.  To  the  internal  surface  of  the 
ramus  of  the  inferior  maxilla  is  attached 

Masseter  interims,  which  arises  from  the  under  surface 
of  the  crus  of  the  sphenoid  bone  and  of  the  palatine  bone, 
and  becomes  attached  below  to  the  greater  part  of  the 
internal  surface  of  the  ramus. 

By  division  of  its  inferior  attachment  we  expose  the 
inferior  maxillary  division  of  the  fifth  cranial  nerve, 
which  emerges  from  the  cranium  through  the  anterior  part 
of  the  foramen  lacerum  basis  cranii.  It  sends  a  large 
bunch  of  fibres  to  join  with  the  seventh  nerve,  and  pass 
over  the  cheek  to  form  the  facial ;  just  before  arriving  at 
the  posterior  maxillary  foramen  it  breaks  up  into  three 
parts — the  buccal^,  gustatory,  and  inferior  dental  branches. 
The  buccal  branch  winds  round  the  front  of  the  coracoid 
process  of  the  bone  and  then  passes  over  buccinator  and 
caninus,  sending  large  branches  to  the  molar  salivary 
glands.  Just  within  its  origin  and  firmly  attached  to  it  by 
nerve-fibres  is  the  otic  ganglion,  which  receives  motor 
fibres  from  the  seventh  and  sends  different  branches  to  the 
middle  ear.  The  gustatory  branch  receives  an  extremely 
important  branch  (chorda  tympani) ,  which  passes  from  the 
seventh  nerve  during  its  course  through  the  middle  ear. 
It  then  passes  between  masseter  internus  and  pterygoideus, 
and  goes  to  supply  the  posterior  and  lateral  parts  of  the 
tongue  with  common  sensation  and  with  the  special  sense 
of  taste.  It  also  sends  a  very  distinct  branch  to  the 
sub-lingual  salivary  gland.  The  inferior  dental  branch 
at  once  passes  through  the  posterior  maxillary  foramen  ; 
it  then  runs  along  below  the  fangs  of  the  inferior  molar - 
teeth,  between  the  two  plates  of  the  bone,  taking  a  curved 
direction  downwards  and  forwards ;  it  sends  a  large  branch 
to  each  molar  tooth,  and  at  the  anterior  maxillary  foramen 
divides,  one  portion  running  onwards  between  the  plates 
of  the  bone,  to  be  expended  in  supplying  the  canine  and 
three  incisor  teeth  of  that  side,  while  the  other  runs 
through  the  foramen  to  the  lower  lip,  blending  with  a  few 
fibres  from  the  facial  nerve.  The  two  last-mentioned 
nerves  are  separated  from  the  buccal  branch  by 

Pterygoideus,  which  arises  from  the  under  surface  of  the 


SPECIAL   ANATOMY.  125 

pterygoid  bone  and  tlie  crus  of  the  sphenoid,  and  becomes 
inserted  into  the  internal  surface  of  the  neck  of  the  inferior 
maxillary  condyle.  The  upper  extremity  of  the  inferior 
maxilla  should  now  be  removed  by  disarticulation  of  the 
joint,  and  sweeping  a  knife  around  the  coracoid  process 
in  the  temporal  fossa.  It  will  be  thus  shown  that  a  con- 
siderable amount  of  fat  assists  in  filling  up  this  fossa, 
thus  allowing  play  of  the  coracoid  process.  Deficiency  of 
this  fat  causes  that  depression  above  the  eyes  noticeable 
in  old  or  emaciated  horses.  In  addition  we  also  see  in  this 
fossa  the 

Temporalis,  a  muscle  which  passes  from  its  attachment 
to  the  superior  bony  boundary  of  the  temporal  fossa,  ex- 
tending as  far  as  the  parietal  ridges  to  become  inserted 
into  the  inner  surface  of  the  coracoid  process  of  the  inferior 
maxilla.  It  is  sometimes  composed  of  two  distinct  parts, 
and  serves  when  acting  alternately  with  its  fellow  to 
give  the  jaw  the  lateral  motion  necessary  for  the  grinding 
of  the  food ;  when  acting  in  conjunction  with  its  fellow  it 
aids  in  closing  the  mouth. 

Muscles  which  close  the  mouth  : — Masseter  externus, 
masseter  internus,  temporalis,  pterygoideus.  We  have 
now  exposed  the  posterior  part  of  the  orbit,  which  in  the 
horse  consists  of  fibrous  membrane,  the  periorhitale ;  below 
this  is  the  internal  maxillary  artery.  Commencing  at 
the  termination  of  the  external  carotid,  at  the  inner  sur- 
face of  the  temporo -maxillary  articulation,  this  vessel 
takes  a  direct  course  towards  the  sphenoideal  foramen, 
and  having  passed  through  it  gains  foramen  rotundum, 
and  thus  becomes  again  visible  just  below  the  orbit.  It 
takes  a  straight  course  towards  the  maxillary  hiatus,  where 
it  breaks  up  into  three  branches  which  adopt  the  names  of 
the  foramina  of  the  hiatus  through  which  they  pass. 
Before  arriving  at  the  sphenoideal  foramen  this  artery  gives 
of£  deep  temporal  branches  upwards  and  branches  doivn- 
wards  to  masseter  internus.  Also  the  inferior  maxillary 
artery  which  passes  through  the  posterior  maxillary  fora- 
men, and  courses  with  the  corresponding  nerve  between 
the  plates  of  the  inferior  maxilla  supplying  the  lower  teeth, 
and  sending  a  small  branch  outwards  through  foramen 
menti.  In  its  course  below  the  orbit  the  internal  maxil- 
lary artery  gives  off  branches  upiuards  to  the  temporal 
muscle,  and  ocular  branches,  which  run  to  the  eyeball  and 


126  OUTLINES    OF   EQUINE   ANATOMY. 

to  the  appendages  of  the  eye,  also  the  su;pra-or'bital  artery, 
which  passes  iu  a  direction  upwards  to  the  root  of  the 
orbital  process  of  the  frontal  bone  ;  after  passing  through 
the  supra-orbital  foramen  it  breaks  up  in  sup"plying  the 
muscles  of  the  forehead.  A  remarkable  branch  of  this 
artery,  the  lateral  nasal  makes  a  peculiar  twist  before 
piercing  the  internal  orbital  foramen.  By  passing 
through  this  it  is  described  as  gaiiiingthe  nasal  chamber, from 
which  it  passes  through  the  cribriform  plate  of  the  eth- 
moid bone  into  the  olfactory  sinus,  and  after  supplying 
the  olfactory  bulb  it  passes  again  through  the  cribri- 
form plate  and  supplies  the  mucous  membrane  of  the 
superior  meatus  of  the  nasal  chamber.  Some  of  the 
ocular  branches  passing  over  the  lower  margin  of  the 
orbit  anatomose  with  branches  of  the  facial  artery.  The 
internal  maxillary  artery  sends  branches  downward  to 
supply  the  soft  palate,  and  the  buccal  branch  to  the  cheek 
and  the  molar  glands  ;  it  then  breaks  up  into  the  spheno- 
palatine, palato-maxillary,  and  superior  dental  branches. 

The  spheno-palatine  artery,  passing  through  the  foramen 
of  the  same  name,  gains  the  nasal  chamber,  where  it  sup- 
plies the  inferior  and  middle  meatus.  The  palato-maxillary 
artery,  on  emerging  from  the  palatine  canal  through  the 
palatine  foramen,  courses  its  way  along  the  lateral  part  of 
the  hard  palate,  and  bending  inwards  anteriorly  is  retained 
in  position  by  a  small  cartilaginous  hook,  and  anastomoses 
with  its  fellow,  the  arch  so  formed  giving  off  a  branch 
which  passes  through  foramen  incisivum  to  anastomose 
with  the  terminal  parts  of  the  superior  labial  arteries.  The 
superior  dental  artery  passes  through  canalis  infra  orbitale, 
and  sends  a  branch  to  each  molar ;  it  sends  a  small  branch 
through  the  infra-orbital  foramen  to  anastomose  with  the 
arteries  of  the  face,  but  the  main  trunk  runs  between  the 
plates  of  the  bones  to  supply  the  tush  and  the  incisors. 

The  fifth  cranial  nerve,  pars  trigemini,  arises  by  two 
roots  from  the  lateral  part  of  the  pons  Varolii  at  the 
base  of  the  brain.  One  of  these  is  sensory,  the  other  is 
motor  ;  in  this  respect  the  nerve  resembles  those  given  off 
from  the  spinal  cord  ;  it  is  hence  sometimes  called  the  spinal 
nerve  of  the  brain,  and  the  analogy  is  increased  by  the 
presence  of  a  large  ganglion,  the  Gasserian,  on  the  sensory 
root.  This  ganglion  is  situated  between  the  two  folds  of 
dura  mater,  which  constitute  the  membranous  tentorium, 


SPECIAL   ANATOMY.  127 

and  tlie  motor  root  runs  over  its  under  surface.  From  the 
ganglion  three  branches  pass  : — One  runs  to  combine  with 
the  motor  tract  to  form  the  inferior  maxillary  division, 
which  passes  through  foramen  lacerum  basis  cranii,  as 
ah'eady  noticed ;  another,  the  ophthalmic  division,  passes 
through  foramen  lacerum  orbitale,  in  company  with  the 
third,  fourth,  and  sixth  cranial  nerves  and  the  ophthalmic 
artery,  and  thus  gains  the  orbit.  The  third,  or  superior 
maxillary  division,  passes  from  the  cranium,  and  emerges 
with  the  internal  maxillary  artery  through  foramen  rotun- 
dum.  It  may  be  seen  with  this  vessel  passing  to  the  maxil- 
lary hiatus,  prior  to  gaining  which  it  divides  into  three  parts, 
corresponding  to  the  terminal  branches  of  the  artery.  The 
superior  dental  hranch  passes  through  canalis  infra-orbitale, 
and,  like  the  artery,  supplies  the  upper  teeth  ;  but  a  very 
large  branch  passes  through  the  infra-orbital  foramen, 
where  it  is  covered  by  levator  labii  superioris  alaeque  nasi. 
It  blends  with  a  large  branch  from  the  facial  nerve,  forming 
the  superior  labial  nerve,  and  the  plexus  of  7ierves  over  the 
lateral  part  of  the  muzzle  formed  hy  the  union  of  the  infra- 
orbital, anterior  maxillary,  and  facial  nerves  corresponds  to 
the  "pes  anserinus  "  of  the  human  subject  The  palato- 
maxillary nerve,  passing  with  the  artery  of  the  same  through 
the  palatine  canal,  gains  the  hard  palate,  which  it  supplies 
with  sensation  ;  it  also  sends  fibres  to  the  soft  palate.  The 
spheno-palatine  nerve,  passing  with  the  spheno -palatine 
artery  through  the  foramen  of  the  same  name,  gains  the 
nasal  chamber,  the  inferior  and  middle  meatus  of  which  it 
supplies  with  common  sensation.  At  its  origin  it  forms  a 
close  connection  by  means  of  numerous  fibres  with  the 
spheno-palatine  or  Meckel's  ganglion,  a  collection  of  nerve- 
cells,  which  receives  motor  fibres  through  the  vidian  branch 
of  the  seventh  cranial  nerve,  and  is  supposed  to  send 
efferent  fibres  to  the  palate. 

We  have  now  exposed  the  mouth,  a  cylindrical  cavity 
elongated  in  an  antero-posterior  direction,  presenting  four 
surfaces  and  two  extremities.  The  anterior  extremity  is 
guarded  by  the  lips,  between  which  is  the  labial  fissure. 
The  posterior  extremity  presents  the  anterior  opening  of  the 
fauces,  bounded  on  either  side  by  the  reflections  of  mucous 
membrane  from  the  palate  to  the  base  of  the  tongue,  the 
posterior  pillars  of  the  tongue.  Through  this  opening  the 
pendulous  palate  and  the  cavities  of  the  tonsils  are  visible. 


128  OUTLINES    OF    EQUINE    ANATOMY. 

The  lateral  surfaces  of  the  mouth  are  formed  by  the  cheeks, 
the  mucous  membrane  lining  these  presents  j^erforated 
papillse,  on  which  the  ducts  of  the  buccal  glands  pour  the 
secretions  of  those  glands  ;  varying  in  position  in  different 
subjects,  but  generally  about  opposite  the  space  between 
the  second  and  third  molar  teeth,  we  may  distinguish  the 
opening  of  the  parotid  duct  with  a  larger  papilla.  The 
mucous  membrane  posteriorly  is  reflected  inwards  behind 
the  molar  teeth  to  join  the  posterior  pillars  of  the  tongue  ; 
in  some  places  it  is  coloured  by  pigmentary  deposit.  On 
the  roof  of  the  mouth,  centrally,  it  is  thick,  and  presents 
dense  stratified  epithelium  and  a  plentiful  submucous 
tissue,  in  which  is  situated  a  remarkable  plexus  of  veins  con- 
gestion of  which  from  dental  or  other  irritation  causes  that 
prominence  of  this  part  termed  "lampas"  by  individuals 
who  ignorantly  considered  it  a  primary  diseased  condition  ; 
on  either  side  of  this  runs  a  palatine  artery,  as  has  been 
described.  That  portion  of  the  mucous  membrane  which 
is  attached  to  the  bony  palate  is  termed  the  hard  palate, 
and  inferiorly  presents  a  central  groove,  from  which 
crescentic  prominences,  seventeen  to  eighteen  in  number 
on  each  side,  run  in  an  oblique  direction  outwards.  These 
are  termed  the  "bars,"  and  are  straightest  and  closest 
posteriorly,  where  they  blend  with  the 

Soft  palate,  the  mucous  membrane  of  which  is  redder 
and  less  dense,  and  which  runs  in  a  backward  direction 
from  the  posterior  crescentic  margin  of  the  x^a^latine  bones. 

Occupying  the  outer  circumferent  margin  of  the  roof 
and  of  the  floor  of  the  mouth  at  particular  parts  we  see  the 
teeth.  These  are  products  of  mucous  membrane.  They 
are  hard  organs  ;  by  some  anatomists  considered  as  bones, 
but  are  merely  the  result  of  special  development  of  mucous 
membrane.  They  are  firmly  fixed  in  cavities  in  bone 
termed  alveolar  cavities,  and  are  surrounded  by  mucous 
membrane  termed  the  gums.  They  present  three  parts  :  — 
A  fang,  th^it  part  enclosed  in  the  alveolar  cavity;  crown, 
that  visible  on  inspection  of  the  mouth  after  the  teeth  are 
fully  developed ;  neck,  that  part  connecting  the  fang  and 
the  crown,  and  to  which  the  mucous  membrane  formmg 
the  gum  is  attached.  Teeth  are  composed  of  three  sub- 
stances (two  of  which  closely  resemble  bone  in  histo- 
logical structure),  dentine,  enamel,  and  crusta  petrosa  or 
cement.     They  surround  a  central  cavity,  which  is  called 


SPECIAL   ANATOMY.  129 

the  pulp  cavity,  for  it  contains  a  small  papilla  to  wliicli  an 
artery  and  a  nerve  run  and  from  wliicli  a  vein  proceeds  ; 
this  is  the  pulp.  It  is  immediately  surrounded  by  dentine, 
which  is  formed  continuously  from  its  outer  part,  so  that 
the  pulp  cavity,  which  is  large  in  the  young  animal,  in  the 
adult  becomes  almost  obliterated  ;  on  the  outer  surface  of 
the  dentine  rests  a  layer  of  very  dense  white  substance  of  a 
petrous  nature,  enamel.  It  is  deficient  on  the  lower  part 
of  the  fang.  Externally  placed  to  this  we  see  a  yellowish- 
brown  matter,  crusta  petrosa  or  cementum.*  The  upper 
surface  of  the  tooth  generally  presents  one  or  more  depres- 
sions, the  infundibuli,  into  which  dip  the  three  layers  of 
substance  of  which  the  tooth  is  composed,  and  which  are 
frequently  filled  with  crusta  petrosa.  When  a  tooth  is 
wholly  covered  on  its  external  surface  with  enamel  it  is 
termed  a  simple  tooth,  all  other  teeth  are  compound.  We 
see  simple  teeth  in  the  dog  ;  the  canines  of  the  horse  are 
by  some  considered  simyjle.  Teeth  are  named  according  to 
their  function,  grinders  and  pincers.  These  are  arranged 
in  rows,  each  of  which  consists  of  six  teeth,  and  between 
the  rows  of  grinders  and  pincers  in  the  horse  are  situated 
solitary  teeth,  the  canines,  cuspidati,  or  tushes,  which  in  the 
mare  are  rudimentary;  they  are  weapons  of  offence  or  of 
defence,  and  are  well  developed  in  stallions.  The  incisors 
or  pincers  are  situated  in  the  mouth,  anteriorly  in  contact 
with  the  inner  surface  of  the  lips,  arranged  along  the 
anterior  crescentic  margin  of  the  hard  palate  ;  a  corre- 
sponding number  being  placed  in  the  upper  margin  of  the 
lower  jaw,  three  incisors  on  each  side  of  the  symphysis. 
The  upper  incisors  are  larger,  longer,  and  put  in  their 
appearance  later  than  those  of  the  lower  jaw.  The  cutting 
surface  of  the  teeth  is  ovoid,  with  an  acute  angle  at  either 
extremity  ;  the  anterior  edge  is  higher  than  the  posterior, 
and  the  tooth,  taken  as  a  whole,  presents  a  curve  the  con- 
cavity of  which  is  posteriorly  situated.  There  are  two 
complete  sets  of  incisors,  temporary  or  milk,  and  perma- 

*  Crusta  petrosa  in  structure  exactly  resembles  bone  presenting 
laminse,  lacunse,  and  canaliculi,  and,  where  it  is  very  thick,  Haversian 
canals.  Dentine  consists  of  an  earthy  matrix,  through  which  branch- 
ing and  wavy  canaliculi  run  from  the  pulp  cavity,  and  near  its  outer 
surface  terminate  in  lacunse.  Enamel  consists  of  prismatic  hexagonal 
bodies,  which  have  their  margins  jagged  to  enable  them  to  fit  closely 
together.  One  extremity  of  these  looks  towards  the  pulp  cavity,  the 
other  towards  the  surface  of  the  tooth. 

9 


130  OUTLINES    or    EQUINE    ANATOMY. 

nent.     These  are  distinguisliable  by  the  following  charac- 
teristics : — Milk  teeth  are  snialler  and  whiter  than  perma- 
nent, and  their  infundibuluin  is  more  shallow  ;  they  have  a 
marked  neck,  and  are  smooth  on  the  anterior  surface  of  the 
crown  ;  permanent  incisors  decrease  in  size  gradually  from 
the  nipping  surface  to  the  extremity  of  the  fang,  and  pre- 
sent grooves  on  their  anterior  surface,  running  in  a  direc- 
tion from  above  downwards.     At  an  early  period  of  foetal 
life  there  may  be  distinguished  the  smooth  margin  of  the 
jaw  covered  by  mucous  membrane.     A  longitudinal  groove 
shortly  presents  itself,  and  at  the  bottom  of  this  "primitive 
dental  groove  "  mucous   papillse  appear.     These  are  pro- 
duced by  a  thickening  of  the  mucous  corium,  which  causes 
an  elevation  of  the  epithelial  and  basement  layers.    Trans- 
verse partitions   (which   subsequently   become   converted 
into   bone)  are  thrown  across  the  groove,  whereby  il  is 
separated  into  as  many  cavities  as  it  subsequently  produces 
teeth  {follicular  stage) .  Then  by  gradual  closure  of  the  upper 
part  of  the  groove,  by  approximation  of  the  margins,  each 
papilla  becomes  enclosed  in  a  sac  {saccular  stage),  which  is 
lined   by   epithelial   cells.     The   parietal  portion   of    the 
epithelial   layer  is  said  to   produce    the    crusta  petrosa, 
the   visceral*  (that    clothing    the    papilla)    epithelium    is 
converted   into   enamel,   and   the   corium  is  continuously 
developed  into  dentine,  that  part  which  has  not  yet  been 
changed  being  termed  the  dental  pulp.     The  papilla  thus 
altered  becomes  too  large  for  its  cavity  and  forces  its  way 
through  the  gum  which  forms  the  upper  wall  of  the  sac 
{eruptive  stage  or  "  cutting  the  teeth'').     Small  portions  of 
the  dental  sac  are  separated  from  the  main  cavity  at  an 
early  stage  of  the  developmental  process,  in  those  cases 
where'  a  second  or  permanent  set  of  teeth  will  be  required 
to  replace  the  temporary  organs.      These  small  sacs  are 
termed  cavities  of  reserve,  and  slowly  undergo  the  changes 
above  described  in  connection  with  the  parent  sac,  a  papilla 
being   produced   which   subsequently   becomes   developed 
into  a  permanent  tooth,  by  the  growth  of  which  absorption 
of  the  fangs  of  the  temporary  teeth  is  brought  about,  and 
they,  being  deprived  of  their  source  of  nutriment,  fall  from 
the  mouth   {''shedding  the  milh  teeth'').     Of  the  molars, 
the  three  anterior  of  each  row  only  are  replaced,  for  in  the 
jaw  of  the  young  animal  there  is  not  room  enough  for  six 
molars.     Those  teeth  which   occupy  the   three   posterior 


SPECIA.L   ANATOMY. 


131 


alveolar  cavities  are  developed  late,  and  remain  tln'oughout 
life,  the  sixth  or  posterior  one  not  appearing  until  tlie 
three  anterior  (temporary)  molars  have  been  replaced,  as 
the  following  table  indicates — 


Temporary. 

Permanent 

1st  incisor 

At  birth 

2  years  6  months 

2nd     „ 

6  weeks 

3      „     6       „ 

3rd       „ 

9  months 

4      „     6 

Tushes 

— 

4      „     6 

1st  molar 

At  birth 

2      „     6 

2ud     „ 

,j 

2      „     9 

3rd      „ 

„ 

3       „     6 

4th      „ 

— 

1  year     3 

5th      „ 

— 

1      „       9 

Gth      „ 

— 

4  years  6 

Variations,  however,  occur  as  a  result  of  breed,  manage- 
ment, &c.  TJioroughhred  horses  date  their  birth  from  the  Isf 
January,  all  other  breeds  from  the  1st  May. 

The  molars  are  developed  from  compound  papill?R. 
Thej  are  found  in  four  rows  of  six  each,  one  on  either  side 
of  the  upper  and  lower  jaws.  Each  molar  presents  six 
surfaces  :  —The  anterior  is  smooth,  in  contact  with  the 
tooth  in  front  through  the  medium  of  the  thm  plate,  form- 
ing the  anterior  boundary  of  the  alveolar  cavity.  But  in 
the  first  molar  this  margin  is  sharp.  TlhQ  posterior  surf  ace  is 
in  similar  contact  with  the  tooth  behind,  but  in  the  last 
molar  is  sharp.  The  external  surface  presents  two  grooves 
running  from  above  downward,  of  which  the  anterior  is  the 
deepest ;  the  internal  surface  is  also  grooved,  but  less  dis- 
tinctly, the  outer  surface  of  the  upper,  the  inner  surface  of  the 
lower,  molar  is  the  largest,  for  the  superficial  or  grinding 
surface  in  both  the  upper  and  lower  molars  slants  obliquely 
downwards  and  outwards,  so  that  the  inner  part  of  the 
upper  comes  in  contact  with  the  outer  part  of  the  lower 
molars,  a  consequence  of  the  greater  width  of  the  superior 
than  of  the  inferior  maxilla ;  so  in  rasping  a  horse's  teeth 
the  rasp  must  be  applied  to  the  inner  edge  of  the  lower, 
the  outer  edge  of  th3  upper,  grinders.  The  grinding 
surface  presents  the  edges  of  the  layers  of  the  substances 
of  which  the  tooth  is  composed  arranged  "  in  the  form  of  a 
Gothic  B,"  so  that,  as  substances  of  different  degrees  of 
durability  are  exposed  to  equal  attrition,  an  irregular 
surface  favorable  to  the  comminution  of  the  food  is  con- 


132  OUTLINES    or   EQUINE   ANATOMY. 

stantly  maintained.  The  superior  molars  present  a  square, 
the  inferior  an  oblong  grinding  surface.  The  deep-seated 
surface  presents  deep  pulp  cavities  into  which  the  portions 
of  the  divided  pulp  fit. 

In  some  cases  premolar  or  ^^  wolves  teeth^'  may  be  found 
fixed  in  the  jaw  in  contact  with  the  anterior  surface  of  the 
first  molar.  They  are  small  portions  of  tooth  substance, 
generally  forced  out  by  growth  of  the  permanent  molars, 
which  occupy  more  room  than  the  temporary.  The 
canines,  tushes,  or  cuspidati  are  four  in  number  in  the 
male,  and  occupy  the  space  between  the  molars  and 
incisors,  being  about  equidistant  from  both.  The  inferior 
canines  are  more  anteriorly  situated  than  the  superior. 
These  teeth  present  no  inf undibula,  but  have  a  single  fang, 
and  their  crown  terminates  in  a  point  at  its  fi'ee  extremity, 
at  which  two  ridges  which  separate  it  into  two  surfaces 
terminate.  The  external  surface  is  convex  in  every  direc- 
tion ;  the  internal  surface  presents  a  groove  surrounding  a 
prominence.  This  is  the  condition  of  the  unworn  tooth  ;  in 
the  mouth  of  the  old  animal  the  crown  becomes  conical  and 
blunted.  In  the  mare  these  teeth  may  be  sometimes  seen  just 
emerging  from  the  gum,  or  simply  as  a  papilla  changed  into 
tooth  substance  on  the  surface  of  the  mucous  membrane. 

The  floor  of  the  mouth  therefore  anteriorly  and  on  either 
side  presents  teeth,  and  the  mucous  membrane  from  the 
lower  margin  of  the  cheeks  and  lower  lips  is  reflected 
upwards  to  form  the  gum,  and  from  the  teeth  on  the  inner 
side  after  passing  for  a  short  distance  downwards  it  is  re- 
flected upwards  to  cover  the  tongue,  which  occupies  the 
central  part  of  the  floor  of  the  mouth.  In  doing  so  it 
forms  a  marked  fold  at  the  central  line  anteriorly,  which 
serves  to  prevent  too  free  play  of  the  tip  of  the  tongue,  run- 
ning upwards  from  against  the  symphysis  of  the  lower  jaw 
and  enclosing  a  portion  of  the  two  genio-hyoglossi  muscles. 
This  is  the  anterior  pillar  or  fraenum  linguae ;  on  either 
side  of  it  may  be  distinguished  an  opening  of  a  submaxil- 
lary salivary  '(Wharton's)  duct,  guarded  by  a  papilla 
termed  the  "  barb." 

The  tongue  is  the  organ  of  the  special  sense  of  taste,  and 
is  prismatic  and  thick  posteriorly,  and  terminates  in  a 
rounded  spathulate  extremity  anteriorly.  Its  bulk  consists 
mainly  of  muscular  structure  mixed  with  the  fibres  of 
which  is  much  fat.     Against  the  superior  surface  the  fatty 


SPECIAL    ANATOMY.  133 

and  muscular  structures  become  intimately  blended  with 
the  deep  surface  of  the  mucous  membrane,  thus  constituting 
a  somewhat  firm  layer  into  which  some  of  the  more  definite 
muscles  are  inserted.  The  mucous  membrane  of  the  lateral 
part  of  the  tongue  presents  several  small  papillae  on  which 
the  ducts  of  the  sublingual  salivary  glands  open.  These  may 
be  seen  as  thin  white  threads  running  from  the  glands,  on 
elevation  of  the  mucous  membrane.  Superiorly  to  these 
we  see  somewhat  large  fungiform  papillse,  so  named  from 
their  resemblance  to  a  mushroom  in  shape.  These  are 
found  only  on  the  lateral  parts  of  the  tongue,  and  on  their 
surface  present  filiform  papillae,  larger  specimens  of  which 
may  be  found  on  the  major  part  of  the  dorstim  or  upper 
surface  of  the  tongue  to  which  they  communicate  the  pecu- 
liar velvety  feel.  They  are  hair-like  prolongations  of  the 
mucous  membrane,  and  are  either  simple  or  compound.  The 
anterior  part  of  the  dorsum  of  the  tongue  presents  a 
central'  fissure,  the  result  of  the  frequent  longitudinal 
folding  of  this  portion  of  the  organ.  The  anterior  edge  of 
this  part  is  rounded  and  the  inferior  surface  along  the 
central  line  presents  the  attachment  of  the  fraenum.  The 
posterior  part  of  the  dorsum  surface  of  the  tongue,  elevated 
above  the  anterior  part,  presents  two  remarkable  round 
spots  which,  on  examination,  prove  to  be  collections  of 
fungiform  papillae  surrounded  by  a  deep  groove  (circum- 
vallate  papillae).  These  are  situated  centrally  about  an 
inch  from  each  other.  A  smaller  one  may  be  sometimes 
seen  just  behind  them. 

We  must  now  examine  the  hyoid  bone  or  bone  of  the 
tongue.  This  forms  the  basis  of  attachment  of  the  pha- 
rynx, larynx,  and  other  structures  situated  in  this  neigh- 
bourhood. It  is  suspended  from  the  under  surface  of 
the  cranium,  and  hangs  between  the  rami  of  the  in- 
ferior maxilla.  It  consists  of  five  distinct  portions :  a 
main  portion  and  four  cornua.  The  main  portion  closely 
resembles  a  hunting  spur,  being  composed  of  a  spur 
process,  running  in  an  anterior  direction,  and  two  heel 
processes,  which  diverge  from  each  other  and  run  backwards 
about  three  inches,  "  forming  a  crescentic  space  between 
them."  These  two  processes  terminate  posteriorly  each  in 
a  point  which  is  continuous  with  the  free  extremity  of  the 
cornu  of  the  thyroid  cartilage.  They  present  a  superior 
sharpened  margin  for  muscular  attachment,  and  an  inferior 


134  OUTLINES    OF    EQUINE    ANATOMY. 

margin  to  which  the  thyro-hyoid  ligament  and  muscle  are 
attached.  To  their  outer  surface  posteriorly  is  attached 
hyo-thyro-pharyngeus  a  constrictor  of  the  pharynx. 
The  spur  and  heel  processes  are  connected  together 
by  the  body  of  the  hone,  which  presents  two  surfaces  and 
four  borders.  To  the  'posterior  border  hyo-epig'lottideus 
runs  from  the  base  of  the  epiglottis,  and  the  thyro-hyoid 
ligament  is  attached.  From  the  anterior  horder  the  spur 
process  projects.  The  lateral  borders  posteriorly  give  rise 
to  the  heel  processes,  anteriorly  present  circular  synovial 
articulatory  surfaces  which  look  in  a  forward,  upward,  and 
outward  direction  ;  to  these  the  inferior  extremities  of  the 
short  cornua  are  attached.  The  superior  surface  of  the  body 
and  the  upper  sharpened  border  of  the  spur  process  afford 
attachment  to  retractor  lingualis,  an  obscure  muscle,  the 
fibres  of  which,  imbedded  in  the  fatty  substance  of  the 
tongue,  influence  its  movements.  The  inferior  surface  of  the 
body  receives  the  superior  terminal  portions  of  suibscapulo- 
hyoideus  and  sterno-thyro-hyoidens.  The  inferior  sharp- 
ened border  of  the  spur  process  affords  attachment  to  mylo- 
hyoideus  and  its  extremity,  which  is  its  deepest  part,  to 

Genio  hyo-glossus,  the  muscle  which  lies  in  contact 
with  its  fellow  at  the  central  plane  of  the  tongue,  and 
which,  being  attached  to  this  point  and  to  the  symphysis 
of  the  inferior  maxilla,  sends  fibres  in  a  radiating  direction 
upwards  to  become  lost  in  the  musculo-adipose  matter  of 
the  tongue  as  far  forward  as  its  tip. 

Genio -hyoideus  also  runs  from  the  anterior  extremity  of 
the  spur  process  of  the  os  hyoides.  It  becomes  attached  an- 
teriorly to  the  symphysis  of  the  jaw,  and  lies  in  contact  with 
its  fellow  in  the  central  line  of  the  inter-maxillary  space. 

Extending  in  an  oblique  direction  foi-wardsand  upwards 
from  the  synovial  articulatory  surfaces  of  the  latera,l  parts 
of  the  body  of  the  hyoid  bone  are  the  short  cornua,  cylin- 
drical portions  of  bone  shorter  than  the  heel  processes, 
s-nallest  at  the  centre,  superiorly  connected  by  fibro- carti- 
lage {in  which  is  generally  to  he  found  a  bony  nodule  analo- 
gous to  the  middle  cornu  of  the  ox)  to  the  inferior  extremity 
of  the  long  cornu.  These  are  embedded  in  the  base  of  the 
tongue  and  are  connected  together  by  the 

Hyoideus  transversus,  which  runs  from  the  internal 
surface  of  one  short  cornu  to  that  of  the  other. 

Hyoglossus  brevis,  the  fibres  of  this  muscle  arise  from 


SPECIAL   ANATOMY.  135 

tlie  wliole  lengtli  of  tlie  lateral  part  of  the  main  portion  of 
the  hyoid  bone,  and  radiate  from  this  toward  the  under 
surface  of  the  mucous  membrane  of  the  base  of  the  tongue. 
Under  this  muscle,  and  so  closely  blended  with  it  as  to  be 
distinguished  only  by  the  direction  of  its  fibres  which  run 
in  a  parallel  direction  forwards,  is 

Hyoglossus  parvus,  arising  from  the  junction  of  the  long 
and  short  cornua  of  the  hyoid  bone,  and  blending  with  hyo- 
glossi  magnus  and  brevis  in  the  substance  of  the  tongue. 
To  the  posterior  margin  of  the  short  cornua  and  of  the 
inferior  extremity  of  the  long  cornu  the 

Hyoideus  parvus  is  attached,  and  runs  obliquely  down- 
wards and  backwards  to  the  superior  margin  of  the  heel 
process. 

The  long  cornu  (of  which  there  is  one  on  each  side)  runs 
obliquely  upwards  and  backwards  from  the  superior  extre- 
mity of  the  short  cornu.  It  presents  three  angles,  three 
borders,  and  two  surfaces.  It  assumes  the  form  of  an  ex- 
tremely acute  angled  isosceles  triangle,  with  its  apex  down- 
wards and  forwards.  The  inferior  angle  is  connected  by 
fibro-cartilage  with  the  short  cornu,  the  antero- superior 
angle  is  connected  by  fibro-cartilage  with  the  hyoid  process 
of  the  petrous  temporal  bone.  From  the  postero-superior 
angle,  which  is  somewhat  tuberous,  the  hyoideus  magnus 
and  digastricus  (sometimes)  arise. 

Hyoideus  magnus  becomes  inserted  into  the  supero- 
lateral part  of  the  body  of  os  hyoides  by  a  small  tendon, 
the  fibres  of  which  separate,  the  foramen  thus  formed 
being  lubricated  with  synovia  for  the  passage  of  the 
tendon  of 

Digastricus,  which  commences  generally  from  the  styloid 
process  of  the  occiput,  being  blended  with  the  origin  of 
stylo-maxillaris,  forms  a  f  asiform  belly,  and  then  a  thin 
round  tendon  which  plays  through  that  of  hyoideus  magnus, 
and  terminates  in  the  second  muscular  portion  which  runs 
forwards,  becoming  inserted  into  the  inferior  margin  of  the 
lower  jaw  as  far  forward  as  the  symphysis.  The  concavity 
of  this  muscle  therefore  is  anteriorly  situated.  The 
anterior  margin  of  the  long  cornu  presents  a  deep  curve 
superiorly,  where  the  mucous  membrane  of  the  guttural 
230uch  is  reflected  from  the  internal  surface  to  the  external 
surface  of  the  bone.  To  the  lower  part  of  the  internal  sur- 
face^ however,  hyo-pharyngeus  becomes  attached,  and  from 


lo6  OUTLI^vES    OF    EQUINE    ANATOMY. 

a  ridge  running  across  the  lower  part  of  the  external  sur- 
face^ a  long  fusiform  muscle — 

Hyoglossus  longus — runs  forwards  along  the  lateral  part 
of  the  tongue,  immediately  beneath  the  mucous  mem- 
brane. 

The  superior  margin  is  the  shortest,  and  affords  attach- 
ment to 

Stylo -hyoideus,  which  arises  from  the  styloid  process  of 
the  occiput,  and  becomes  inserted  into  the  superior  margin, 
and  external  surface  of  the  extreme  upper  part  of  the  long 
cornu. 

.The  posterior  margin  is  almost  straight,  between  it  and 
hyoideus  magnus  the  external  carotid  artery  passes 
superiorly ;  and  lower  down  the  twelfth  or  lingual  nerve, 
and  the  submaxillary  artery,  which  on  gaining  the  external 
surface  of  the  long  cornu  gives  off  the 

Lingual  artery,  which  runs  in  a  forward  direction  over 
the  external  surface  of  the  short  cornu,  through  mylo- 
hyoideus,  the  fibres  of  which  separate  for  its  passage,  and 
breaks  up  to  form  the  ranine  and  sublingual  branches. 
The  ranine  runs  to  the  tip  of  the  tongue  between  the 
genio-hyoglossus  and  genio-hyoideus  muscles,  taking  a 
wavy  course,  whereby  it  is  capable  of  adapting  itself  to 
temporary  elongation  of  the  tongue.  It  sends  branches 
downwards  to  anastomose  with  the  superior  branches  of 
the  sublingual,  which,  after  supplying  the  gland  of  the 
same  name,  expends  itself  in  the  muscular  structure  of  this 
neighbourhood.  The  veins  of  the  tongue  correspond  to 
the  arteries,  and  empty  themselves  into  the  submaxillary 
vein.  The  nerves  are  the  gustatory  branch  of  the  inferior 
maxillary  division  of  the  fifth,  and  the  anterior  branch  of  the 
glosso- pharyngeal  {ninth),  ivhich  endoiv  it  with  common  sensa- 
tion, and  with  the  special  sense  of  taste.  It  owes  its  motor 
potver  to  the  twelfth,  lingual,  or  hypoglossal  nerve,  which 
arises  from  the  lateral  part  of  the  medulla  oblongata, 
and  emerges  from  the  cranium,  through  foramen  condyloi- 
deum.  It  passes  over  the  guttural  pouch,  and  runs  in  an 
anterior  direction  between  the  pneumogastric  and  spinal 
accessory  nerves,  over  the  internal  and  external  carotid 
arteries,  and  between  hyoideus  magnus  and  the  long  cornu 
to  the  lateral  part  of  the  tongue. 

By  division  of  the  amphiarthrotic  joint  of  the  hyoid 
long  cornu  with  the  petrous  temporal  bone,  and  bending 


SPECIAL    ANATOMY.  187 

downwards  this  process,  we  expose  the  guttural  pouch. 
This  is  a  dilated  pouch,   lined  by  a  transparent  mucous 
membrane  in  which  we   may  see  vessels  ramifying,  and 
which  has  an  opening  anteriorly  situated,  a  long  slit  in 
the  wall  of  the  Eustachian  tube,  which  here  degenerates 
into  a  mere  groove  between  two  cartilaginous  ^prominences, 
dilated  inferiorly.     It  is  visible  as  far  as   foramen  sty- 
loideum,  and  inferiorly  is  the   only  source  of  communi- 
cation between  the  pharynx  and  the  guttural  pouch.     The 
outer  and  lower  corner  of  the  anterior  surface  of  the  i^ouch 
is  bounded  by  hyo-pharyngeus,  situated   between   stylo- 
pharyngeus  and  palato-pharyugeus  ;  here  also  we  see  the 
parotid  lymphatic  g-lands.    Posteriorly  the  guttural  pouch 
presents  the  superior  attachment  of  the  recti  capitis  antici 
muscles,  on  the  outer  side  of  which  are  large  nerves  and 
the  internal  carotid  artery.     The  pouch  along  the  central 
line  lies  in  contact  with  its  fellow.     It  jDresents  numerous 
papillae  on  its  internal  surface.     By  cutting  through  the 
posterior  pillar  of  the  tongue  we  now  expose  the  isthmus 
of  the  fauces.     This  is  the  passage  which  runs  from  the 
base   of   the   tongue   to   the   epiglottis.     Anteriorly   it  is 
bounded   by   the    opening  between   the  posterior  pillars 
of    the   tongue,    posteriorly   by    the    opening,   on    either 
side  of  which  are  the   pillars  of  the   fauces,   which   are 
composed  of    muscular  fibres  running  directly  from   the 
jDterygoid  process   to    the  thyroid   cornu,  surrounded  by 
mucous  membrane,  much  thickened  by  addition  of  salivary 
glandular  structure.    The  roof  of  this  passage  is  formed  by 
the  soft  palate,  which  consists  of  a  fixed  and  pendulous 
portion.     The  fixed  portion  is  attached  anteriorly  and  late- 
rally to  the  crescentic  posterior  margin  of  the  ossa  palati. 
It  consists  of  a  fibrous  layer,  the  superior  surface  of  which 
is  covered  by  pharyngeal  mucous  membrane,  the  inferior 
separated   by    a    muscular   layer  and   salivary  glandular 
structure  from  the  mucous  membrane  of  the  fauces.     This 
muscular  layer,  palato-pharyngeus,  runs  from  the  fibrous 
layer  and  from  the  pterygoid  process,  to  blend  with  its 
fellow  at  the  central  line  of  the  pharynx,  and  to  become 
attached  to  the  thyroid  cornua.     The  fibrous  layer  is  also 
acted  upon  by 

Tensor  palati,  which  arises  from  the  styloid  process  of 
the  petrous  temporal  bone  in  common  with  stylo- 
pharyngeus,  runs  forwards  along  the  side  of  the  Eustachian 


138  OUTLINES   OF    EQUINE   ANATOMY. 

tube,  to  wliicli  it  is  also  attached,  and  after  passing  through 
the  pterygoid  groove,  where  it  is  bound  down  by  a  liga- 
ment, and  lubricated  by  synovia,  becomes  inserted  into  the 
fibrous  palate,  which  it  serves  to  render  tense. 

The  pendulous  portion  of  the  soft  palate  is  very  large  in 
the  horse,  and  serves  to  close  the  posterior  opening  of  the 
fauces,  except  during  the  passage  of  food.  Its  inferior 
margin  is  somewhat  concave,  and  it  consists  simply  of  two 
layers  of  mucous  membrane,  with  an  intervening  glandular 
layer.  The  floor  of  the  fauces  is  that  portion  of  mucous 
membrane  situated  between  the  base  of  the  tongue  and 
the  epiglottis.  Every  portion  of  the  mncous  membrane  of 
the  fauces  presents  large  papillae  and  openings,  for  it  is 
surrounded  by  the  palatine  salivary  glands.  Its  lateral 
avails  present  depressions  corresponding  to  the  prominences 
termed  tonsils  in  the  human  subject.  The  pharynx  is  an 
elongated  passage  of  mucous  membrane,  into  which  several 
muscles  are  inserted,  and  on  which  they  act.  Superiorly 
the  pharynx  presents  anteriorly  the  tivo  posterior  openings 
of  the  nasal  chamhers,  separated  by  the  inferior  sharpened 
margin  of  the  vomer,  closely  invested  by  mucous  mem- 
brane ;  on  either  side  of  these,  and  more  posteriorly,  are 
elongated  slit-like  openings,  each  guarded  by  a  cartilagi- 
nous valve,  the  o][)enings  of  the  Eustachian  tubes,  through 
which  air  passes  to  the  middle  ears  and  to  the  guttural 
pouches,  more  posteriorly  the  muscular  walls  of  the 
pharynx  lie  in  contact  superiorly  with  the  guttural  pouches. 
Posteriorly  the  commencement  of  the  esoplmgiis  is  the  result 
of  the  gradual  narrowing  of  the  cavity.  The  floor  of  the 
pharynx  is  formed  anteriorly  by  the  upper  surface  of  the 
soft  palate,  posteriorly  by  the  superior  orifice  of  the  larynx  j 
between  the  two  is  the  posterior  opening  of  the  fauces.  The 
muscles  of  the  pharynx  are  either  constrictors  or  dilators. 
Constrictors  :  Hyo-thyro  pharijjigeus,  runs  from  the  posterior 
23art  of  the  heel  process  of  os  hyoides  and  from  the  thyroid 
cornu.  Thyro-pharyngeus,  from  the  lateral  part  of  the 
external  surface  of  the  ala  of  the  thyroid  cartilage.  Crico 
pharyngeus,  from  the  lateral  part  of  ^he  cricoid  cartilage 
(this  muscle  is  directly  continuous  with  the  muscular  layer 
of  the  esophagus).  These  three  muscles  run  upwards  to 
blend  with  their  fellows  and  with  each  other  in  becoming 
inserted  into  the  central  line  of  the  upper  surface  of  the 
pharyngeal  mucous  membrane.    Dilators  :  Hyo -pharyngeus, 


SPECIAL    ANATOMY.  139 

runs  from  tlie  internal  surface  of  the  long  cornu  of  os 
hjoides,  and  blends  with  its  fellow  upon  the  upper  surface 
of  the  pharynx.  Stylo-pharyngeus  arises  in  common  with 
tensor  palati  from  the  styloid  process  of  the  petrous  tem- 
poral bone,  and  also  is  attached  to  the  lateral  part  of 
the  Eustachian  tube ;  it  blends  with  its  fellow  on  the 
wall  of  the  pharynx.  Potato  pharyngeus  has  been  already 
noticed. 

The  pharynx  is  suf)plied  with  blood  by  the  ascending 
pharyngeal  hra^iches  of  the  submaxillary  artery,  and  also  by 
branches  from  the  internal  maxillary.  It  is  partly  supplied 
with  nerve  force  by  the  sympathetic,  partly  by  the  glosso- 
pharyngeal, and  superior  laryngeal  branch  of  the  pneumo' 
gastric.  The  glcsso-pharyngeal  (or  ninth)  cranial  nerve 
arises  from  the  lateral  part  of  the  medulla  oblongata, 
and  in  passing  out  of  the  cranium  by  foramen  lacerum 
basis  cranii  has  a  ganglion  upon  it.  Passing  over  the  wall 
of  the  guttural  pouch  it  has  intimate  connection  with  the 
large  nerves  of  this  neighbourhood  and  with  the  superior 
cervical  ganglion.  It  then  divides,  sending  one  branch  to 
supply  the  posterior  and  lateral  parts  of  the  tongue  with 
common  sensation  and  the  special  sense  of  taste ;  the  other 
to  the  pharynx. 

By  an  incision  in  a  longitudinal  direction  through  the 
face  to  one  side  of  the  central  line  we  may  expose  the 
nasal  chambers,  and  by  remo^'al  of  an  oblong  portion  of 
the  septum  nasi  we  may  expose  the  turbinated  bones  in 
situ.  The  NASAL  CHAMBERS  are  cavities  elongated  in 
a  direction  from  before  backwards,  bounded  anteriorly  by 
the  anterior  nares,  posteriorly  by  the  posterior  nares.  The 
chamber  of  one  side  is  separated  from  its  fellow  inwardly 
by  the  septum  nasi,  a  thick  layer  of  cartilage,  which  is 
attached  along  its  inferior  margin  into  the  groove  of  the 
vomer  ;  posteriorly  to  the  crista  galli  process  of  the  ethmoid 
bone  ;  superiorly  it  bifurcates  and  becomes  spread  out  over 
the  lower  surface  of  the  nasal  bones,  beyond  which  it  ex- 
tends anteriorly,  forming  a  point  in  front  of  the  nasal  peak, 
to  which,  on  either  side,  an  inverted  comma-shaped  piece 
of  cartilage  is  attached,  being  composed  of  the  alal  and 
corneal  cartilages.  The  alal  cartilage  is  circular,  pre- 
senting a  superior  and  an  inferior  surface,  and  from  its 
inner  margin  the  corneal  cartilage  runs  in  a  direction 
forwards,  downwards,  and  outwards.     The  inferior  extre- 


140  OUTLINES    OF    EQUINE    ANATOMY. 

mity  of  the  latter  is  continuous  by  means  of  a  fold  of 
mucous  membrane  witb  the  inferior  turbinated  bone. 

Dilator  naris  anterior  runs  from  the  external  sur- 
face of  one  ala  to  that  of  the  other,  while  the  corneal 
cartilages  are  connected  together  anteriorly  by  a  direct 
continuation  of  it,  by  some  anatomists  termed  cor- 
nealis  transversus.  Dilatores  naris  superior  and  inferior, 
levator  labii  superioris  alseque  nasi,  and  retractor  labii 
superioris,  also  become  attached  to  these  cartilages.  The 
skin  extends  around  the  margin  of  the  nostril,  as  formed 
by  these  structures,  and  is  continued  for  a  short  distance 
in  the  nasal  chamber,  where  it  insensibly  blends  with  the 
mucous  membrane.  About  the  point  of  junction  at  the 
outer  side,  inclined  to  the  superior  part  of  the  nostril  (infero 
internal  in  the  horse),  is  the  anterior-  opening  of  the  ductus  ad 
nasum  which  looks  as  though  "  punched  out  of  the  mucous 
membrane,"  On  the  outer  side  the  common  integument  be- 
comes very  thin,  hairless,  and  prolonged  in  the  angle  between 
the  superior  process  of  the  anterior  maxilla  and  the  free 
margin  of  the  nasal  bones,  to  form  a  blind  pouch,  the  false 
nostril,  which  we  have  found  filled  with  epithelial  layers  of 
cells.  To  the  posterior  extremity  of  this  a  muscle  which  runs 
from  just  above  the  anterior  termination  of  the  zygomatic 
ridge  is  attached,  also  levator  labii  superioris  alseque  nasi. 
Into  this  cavity  the  air  passes  directly  from  the  anterior 
naris  ;  it  has  to  diverge  slightly  inwards  to  gain  the  nasal 
chamber.  The  roof  of  the  nasal  chamber  is  formed  by  the 
inferior  concave  surface  of  the  nasal  bone,  posteriorly  by 
the  nasal  plate  of  the  frontal  bone.  The  outer  wall  pre- 
sents the  two  ossa  turbinata,  by  means  of  which  the  cavity 
is  divided  into  three  meatus. 

The  superior  turbinated  bone  is  attached  to  the  inner 
surface  of  the  nasal  bone,  and  consists  of  a.  thin  plate 
curled  from  above  downwards.  Anteriorly  it  terminates 
by  a  cartilaginous  prolongation,  which  gradually  blends 
with  the  wall  of  the  chamber ;  posteriorly  it  is  directly 
continuous  with  the  lateral  mass  of  the  ethmoid  bone. 
Its  cavity  is  divided  by  a  partition  into  two  parts  ;  the  ante- 
rior helps  to  form  the  nasal  chamber  opening  into  the 
middle  meatus ;  the  posterior  forms  part  of  the  superior 
maxillary  sinus. 

The  inferior  turbinated  bone  is  attached  to  the  inner 
surface  of  the  superior  maxillary  nasal  plate.     It  is  smaller 


SPECIAL   ANATOMY.  141 

than  tbe  superior ;  posteriorly  it  gradually  disappears ; 
anteriorly  it  presents  a  bifid  cartilaginous  prolongation, 
one  of  the  divisions  of  which  runs  to  the  inner,  the  other 
to  the  outer  wing  of  the  nostril.  It  has  also  an  anterior 
and  a  posterior  division  ;  the  former  helps  to  form  the 
middle  meatus,  the  latter  enters  into  the  composition  of 
the  inferior  maxillary  sinus.  Thus  the  superior  meatus, 
the  longest  and  narrowest,  is  between  the  roof  of  the 
chamber  and  the  upper  surface  of  the  superior  turbinated 
bone.  It  extends  from  the  anteiior  naris  to  the  cribriform 
plate.  The  middle  meatus,  between  the  ossa  turbinata, 
comprises  the  anterior  cavities  of  both  turbinated  bones, 
and  extends  from  the  anterior  naris  to  the  ethmoid  cells, 
blending  anteriorly  with  the  superior ;  j^osfei-iorZ?/  it  presents 
the  ope7iing  of  the  sinuses  of  the  head.  The  inferior  meatus 
is  between  the  lower  surface  of  the  inferior  turbinated  bone 
and  the  floor  of  the  chamber ;  it  extends  from  the  anterior 
to  the  posterior  naris,  blending  anteriorly  and  posteriorly 
with  the  middle.  The  Schneiderian  or  pituitary  mucous 
membrane  lines  every  part  of  the  nasal  chamber.  It  is 
highly  vascular  and  thick,  performs  the  part  of  periosteum 
to  the  turbinated  bones  and  ethmoid  lateral  masses,  and 
assumes  almost  an  erectile  character  at  the  anterior  ex- 
tremity of  the  ossa  turbinata.  The  superior  meatus  is 
supplied  by  the  lateral  nasal  artery  and  nerve,  and  the 
inferior  and  middle  meatus  by  the  spheno-palatine  artery 
and  nerve.  The  ethmoid  cells  and  the  posterior  part  of 
the  nasal  chamber,  in  addition,  receive  the  fibres  of  the 
olfactory  nerve,  which  afford  the  special  sense  of  smell. 
These  pass  through  the  foramina  in  the  cribriform  plate  of 
the  ethmoid  bone,  and  are  not  enclosed  in  any  common 
sheath,  but  each  fibre  runs  its  course  independently  after 
its  origin  from  the  olfactory  bulb,  and  terminates  in  a  cell 
on  the  nasal  mucous  membrane.  These  fibres,  examined 
under  the  microscope,  are  found  to  resemble  sympathetic 
fibres,  being  devoid  of  medullary  sheath  and  of  white  sub- 
stance of  Schwann.  The  septum  nasi,  at  its  antero- 
inferior part,  is  continuous  with  the  cartilage  which  fills 
the  incisive  openings,  and  in  which  may  be  found  a  mucous 
organ  resembling  the  duct  of  Stenson,  which  in  the  ox  forms 
a  communication  between  the  nasal  chamber  and  the  cavity 
of  the  mouth.  In  the  horse  it  only  opens  into  the  nasal 
chamber.  '  We  have  traced  it  backwards  above  the   bony 


142  OUTLINES    OE    EQUINE    ANATOMY. 

palate,  as  far  as  the  soft  palate,  where  it  terminated  in  a 
cul-de-sac.  Some  of  the  bones  of  the  head  present  large 
cavities  lined  by  mucous  membrane,  which  is  (normally) 
thin  and  transparent.     These,  the 

Sinuses  of  the  head,  are  five  in  number  on  each  side. 
They  present  numerous  bony  trabeculse  projecting  inwards 
forming  partial  septa,  and  are  best  developed  in  old 
animals,  being  the  result  of  absorption  of  bone.  By  con- 
tainmg  rarefied  air  they  serve  to  lessen  the  weight  of  the 
head,  and  by  causing  bulging  of  the  bone  they  afford  in- 
creased surface  for  muscular  attachment.  The  frontal 
sinus  in  the  bone  of  the  same  name  is  bounded  by  its 
cranial,  nasal,  and  external  plates.  Internally  it  is  separated 
from  its  fellow  by  a  bony  plate.  To  open  this  sinus  we 
draw  a  line  from  the  lower  margin  of  the  orbital  process 
of  one  frontal  bone  to  that  of  the  other ;  bisect  this  line  and 
in  the  angle  so  formed  inferiorly  trephine.  The  sphenoid 
sinus  (which  only  appears  very  late  in  life)  and  the  ethmoid 
sinus  are  cavities  mainly  contained  in  the  bodies  of  the  bones 
of  the  same  names  respectively.  The  antrum  or  superior 
maxillary  sinus  is  formed  by  the  palatine,  superior  maxil- 
lary, malar,  lachrymal,  and  superior  turbinated  bones.  It 
presents  two  bony  cauals  running  through  it — one,  canalis 
infra-orbitale,  through  which  the  superior  dental  artery  and 
nerve  run  ;  the  other  is  the  ductus  ad  nasum,  which  termi- 
nates by  piercing  the  nasal  plate  of  the  superior  maxilla 
several  inches  up  the  nasal  chamber ;  being  continued  by  a 
membranous  duct  which  runs  underneath  the  mucous  mem- 
brane to  its  opening.  The  above  sinuses  open  by  a  common 
foramen  into  the  nasal  chamber,  by  a  very  small  opening  at 
the  posterior  part  of  the  middle  meatus.  The  inferior  max- 
illary sinus  is  more  anteriorly  placed,  and  is  sej)arated 
from  the  superior  maxillary  sinus  by  a  thin  but  imperforate 
plate  which  extends  to  the  opening  into  the  nasal  chamber, 
thus  dividing  it  into  two.  So  this  sinus  does  not  com- 
municate with  the  rest,  all  of  which  communicate  freely 
among  themselves.  To  trephine  this  sinus,  a  line  is  drawn 
parallel  to  the  zygomatic  ridge  about  an  inch  above  it,  and 
the  point  where  this  meets,  a  perpendicular  line  connecting 
the  two  from  the  termination  of  the  ridge,  indicates  the 
point  of  incision. 

The  contents  of  the  orbit  may  be  examined  by  removal  of 
the  superior  and  outer  walls  by  sawing  through  the  rest  of 


SPECIAL   ANATOxMY.  143 

tlie  orbital  process  of  the  frontal  bone,  externally  to  tbe 
supra-orbital  foramen,  and  through  the  lower  part  of  the 
malar  bone.  After  which  the  separated  portion  of  bone  must 
be  raised  by  a  chisel,  and  removed  by  division  of  the  peri- 
orbita,le.  We  are  thus  enabled  to  examine  the  lachrymal 
gland,  a  racemose  glandular  body  flattened  from  above 
downwards,  and  moulded  between  the  under  surface  of  the 
orbital  process  and  the  structures  beneath  ;  it  has  also  an 
accessory  lobule  found  in  the  upper  eyelid.  It  resembles  one 
of  the  salivary  glands  in  appearance,  and  pours  its  secretion 
through  several  small  ducts  upon  the  inner  surface  of  the 
upper  eyelid.  After  passing  over  the  front  of  the  eyeball, 
being  diffused  by  the  winking  action  of  the  eyelids,  the 
tears  (or  lachrymal  secretion)  pass  through  the  canal  formed 
by  approximation  of  their  free  margins  towards  the  inner 
canthus,  to  which  it  is  directed  by  the  downward  and  inward 
inclination  of  the  palpebral  fissure.  By  the  caruncula  lach- 
rymalis  it  is  directed  into  the  puncta  lachrymalia,  openings 
situated  one  at  the  inner  extremity  of  each  eyelid,  and 
from  this  passes  through  a  series  of  membranous  canals  to 
the  anterior  naris.  It  first  gains  the  lachrymal  canals,  one 
of  which  runs  from  each  punctum  in  a  downward  direction  ; 
they  converge  and  just  at  the  lachrymal  foramen  meet  and 
form  the  lachrymal  sac,  from  which  the  ductus  ad  nasum 
runs  through  a  special  canal  in  the  lachrymal  and  superior 
maxillary  bones.  It  may  be  exposed  by  use  of  the  hammer 
and  chisel  and  will  be  found  to  extend  for  about  three  quar- 
ters of  its  course  in  the  bony  canal.  Its  anterior  part  is 
continued  onwards  between  the  bone  and  the  Schneiderian 
membrane  as  far  as  the  anterior  naris,  where  it  opens  at 
the  point  of  junction  of  the  skin  and  mucous  membrane 
at  the  superior  part.  Situated  between  the  caruncula 
lachrymalis  and  the  eyeball  is  the  cartilage -nictitans 
(winkingjmembrane,  or  third  eyelid).  It  is  thickest  pos- 
teriorly, and  at  its  anterior  free  margin  is  covered  by 
mucous  membrane,  which  generally  contains  some  pigment. 
Internally  its  yellow  fibro-cartilaginous  substance  is  con- 
tinuous with  some  yellow  elastic  tissue,  enclosed  in  the 
meshes  of  which,  and  running  among  the  muscles  of  the 
eye,  is  fatty  matter  on  ivhicli  the  movements  of  the  cartilage 
depend,  for  when,  by  the  action  of  its  muscles,  the  eyeball 
is  retracted  it  presses  upon  this  mass  of  fat,  which  in  its 
turn  presses  the  cartilage  over  the  front  of  the  eyeball. 


144  OUTLINES    or    EQUINE    ANATOMY. 

This  fat  is  found  even  in  tlie  most  emaciated  subjects. 
"We  have  already  noticed  the  levator  palpebrae  superioris 
internus  ;  by  incision  through  the  periorbital  we  may  now 
expose  it :  a  thin  layer  of  muscle  which  arises  from  the 
upper  margin  of  the  sphenoicleal  hiatus  and  runs  to  the 
upper  eyelid,  on  which  it  is  enabled  to  act  by  gaining 
leverage  over  the  upper  surface  of  the  eyeball.  The 
periorbitale  is  a  dense  fibrous  membrane  which  lines  the 
orbital  cavity,  forming  the  sole  protection  to  the  contained 
structures  at  the  postero-inferior  and  suj)erior  parts,  which 
in  the  human  subject  are  bony.  Anteriorly  it  is  attached 
to  the  margin  of  the  orbit,  posteriorly  around  the  sphe- 
noideal  hiatus  ;  it  encloses  the  eyeball  and  its  muscles. 
From  around  this  hiatus  other  muscles  arise  and  run  to 
the  eyeball. 

Retractor  oculi,  consisting  of  four  distinct  portions, 
arises  from  directly  around  it,  and  after  passing  in  a 
forward  direction  in  contact  with  the  optic  nerve  becomes 
inserted  into  the  posterior  part  of  the  extei'nal  surface  of 
the  sclerotic  coat.     The  four 

RECTI — externus  or  abductor,  internus  or  adductor, 
superior  or  levator,  and  inferior  or  depressor — arise  from 
the  external,  internal,  superior,  and  inferior  parts  of  the 
spheiioideal  hiatus  respectively,  and  2:>ass  to  the  anterior 
part  of  the  sclerotic,  and  form  aponeurotic  expansions 
which  unite  at  their  margins  respectively,  forming  thus  a 
continuous  layer,  situated  around  the  outer  margin  of  the 
cornea,  covered  anteriorly  by  conjunctiva,  tunica  albuginea 
(forming  the  "  white  of  the  eye  "). 

Superior  oblique  muscle  arises  from  just  above  the 
straight  muscles  at  the  upper  part  of  the  sphenoideal 
hiatus.  It  then  runs  to  the  root  of  the  orbital  process  of 
the  frontal  bone,  where  it  passes  through  a  fibro- cartilagi- 
nous loop.  From  this  it  runs  to  the  upper  part  of  the  eye- 
ball, forms  an  aponeurotic  tendon  which  runs  beneath  the 
tendon  of  levator  oculi,  and  becomes  inserted  into  the 
anterior  part  of  the  sclerotic  between  the  last-mentioned 
muscle  and  abductor  oculi.  Sirangeways  has  noticed  an 
accessory  muscle  which  arises  near  the  fibrous  loop  and  he- 
comes  blended  with  this;  we  have  frequently  verified  this 
observation. 

Inferior  oblique  muscle  arises  from  the  orbital  plate  of 
the  lachrymal  bone,  near   the   lachrymal  foramen,  runs 


SPECIAL   ANATOMY.  143 

outwards  and  becomes  aponeurotic,  is  inserted  into  the 
anterior  paii;  of  the  sclerotic  between  the  abductor  and 
depressor  ;  it  passes  externally  to  the  depressor. 

The  structures  contained  within  the  orbit  receive  blood 
through  the  ocular  branches  of  the  internal  maxillary  artery 
and  through  the  ophthalmic  artery.     The  former  we  have 
already  noticed,  and  of  these  the  most  remarkable,  which 
we  distinguish  are  the  lateral  nasal,  taking  a  peculiar  curve 
through  the  bottom  of  the  orbit,  and  then  passing  into 
foramen   orbitale  internum,   and  the  supra-orhital,  which 
runs  directly  to  the  foramen  of  the  same  name.     Ciliary 
arteries  run  from   the   internal  maxillary  to  the  eyeball. 
The  ophthalmic  artery  arises  in  the  cranial  cavity  from  the 
anterior   communicating    or    from   the    middle    cerebral 
artery.     It  passes   through  foramen   lacerum   orbitale  in 
company  with  several  nerves,  and  on  emerging  from  the 
foramen  gives  off  branches  to  the  lachrymal  gland,  and  to  the 
eyelids,  also  arteria  centralis  retinae,  which  gains  the  eye- 
ball  by   passing   through  the  centre  of  the  optic  nerve. 
Three  nerves  arising  from  the  base  of  the  brain  (nominally) 
supply   the   muscles   of   the   eyeball   with   motor   power. 
Motores  oculorum  or  third  cranial  pair  of  nerves,  arising 
from  the  centre  of  the  under  surface  of  the  crus  cerebrum, 
each   nerve   passes   from   the   cranium   through    foramen 
lacerum  orbitale  and  then  gives  off  fibres  to  all  the  muscles 
except  the    abductor  and  the  superior  oblique   (and  the 
external  part  of  retractor).     From  this  nerve  also  a  branch 
passes  to  the  ophthalmic  or  lenticular  ganglion,  a  small 
collection  of  nerve  cells  found  at  the  point  where  the  third 
nerve  gives  off  fibres  to  the  inferior  oblique  muscle.     It 
receives  sensory  fibres  from  the  lateral  nasal  branch  of  the 
ophthalmic  division  of  the  fifth,  and  sends  ciliary  branches 
to  the  eyeball.     The  ophthalmic   division  of  the    fifth 
cranial   nerve,    passing    from    the    gasserian    ganglion, 
emerges  from  the  cranium  through  foramen  lacerum  orbi- 
tale, it  then  breaks  up  to  supply  the  structures  of  the  eye 
and   its   appendages   with   common    sensation.      Among 
others,  giving  off  the  supra-orbital  and  lateral  nasal  nerves, 
which  follow  the  course  of  the  arteries  of  the  same  name. 
The  lateral  nasal  affords  the  sensory  root  of  the  ophthalmic 
ganglion.     The  pathetic  or  fourth  nerve  arises  from  the 
valve  of  Yieussens,  which  forms  the  anterior  part  of  the  roof 
of  the  fourth  ventricle   of    the    brain.     These   are    the 

10 


146  OUTLINES    OF    EQUINE    ANATOMY. 

smallest  nerves  at  tlie  base  of  the  brain,  and  wind  round 
the  outer  surface  of  the  crura  cerebri,  puttinsr  in  their 
appearance  just  in  front  of  the  pons  Varolii.  They  gene- 
rally are  found  emerging  from  the  cranium  through 
foramen  lacerum  orbitale  (and  not  through  foramen 
pathetici  as  their  name  might  lead  us  to  expect,  and  which 
only  gives  passage  to  small  vessels).  These  nerves  run 
direct  to  the  superior  oblique  muscles  to  which  they  give 
motor  power. 

Abducens  or  sixth  pair  of  nerves  arise  from  the  under 
surface  of  the  medulla  oblongata,  just  behind  the  pons 
Varolii,  on  either  side  of  the  inferior  longitudinal  fissure. 
Each  nerve  passes  through  foramen  lacerum  orbitale  in 
company  with  the  third,  fourth,  and  ophthalmic  division  of 
the  fifth  nerves,  and  the  ophthalmic  artery  of  the  side  to 
which  it  belongs,  and  on  gaining  the  orbit  runs  to  supply 
the  abducens  muscle. 

The  eyeball  or  globe  of  the  eye  is  a  spherical  body, 
slightly  flattened  from  before  backwards.  The  posterior 
three  fourths  is  formed  by  a  white  fibrous  coat,  the  sclerotic, 
its  anterior  part  by  a  transparent  layer,  the  cornea.  To  its 
postero-inferior  and  internal  part  runs  the  optic  nerve, 
enclosed  in  its  dense  sheath  of  dura  mater.  The  eyeball 
presents  three  coats,  three  cavities,  and  three  humours, 
with  accessory  parts.  The  sclerotic  is  a  fibrous  coat,  which 
is  externally  situated  at  the  posterior  three  fourths  of  the 
eyeball.  It  is  thickest  posteriorly,  and  grows  thinner  to 
about  the  centre,  when  again  it  commences  to  grow  thick, 
and  anteriorly  the  cornea  fits  into  it  "  like  a  watch-glass 
into  its  case.  Around  the  opening  of  the  optic  nerve  it 
becomes  attached  to  its  sheath,  which  becomes  inflected 
inwards  forming  a  plate,  lamina  cribrosa, through  numerous 
perforations  in  which  the  fibres  of  the  nerve  pass.  Through 
the  largest  of  these  perforations,  termed  the  porus  opticus, 
the  arteria  centralis  retinae  passes.  Numerous  small  fora- 
mina, through  which  the  ciliary  nerves  and  vessels  pass, 
are  to  be  seen  on  the  surface  of  the  sclerotic.  Anteriorly 
it  is  directly  continuous  with  the  cornea,  so  that  we  cannot 
distinguish  between  them  with  the  microscope,  though 
the  transparency  of  the  cornea  is  sufficiently  distinctive, 
and  seems  to  be  due  to  fluid  contained  between  its  laminae, 
since  opacity  is  caused  by  pressure.  It  is  a  segment  of  a 
smaller  sphere  than  the  sclerotic,  which  overlaps  it  most 


SPECIAL   ANATOMY.  147 

superiorly  and  inferiorlj,  so  the  part  visible  in  the  living 
animal  is  markedly  ovoid  in  shape,  the  largest  end  being 
the  inner.  Around  its  outer  circumferent  margin  we  may 
observe  a  semi-opaque  ring,  arcus  senilis  caused  by  the 
presence  of  the  ciliary  ligament  internally  to  this  part.  It 
consists  of  two  parts,  cornea  propria  and  cornea  elastica ;  the 
former  is  anteriorly  placed,  and  its  structure  may  be  divided 
into  several  laminae  ;  the  latter,  posteriorly  placed,  consists 
of  a  single  lamina.  The  anterior  surface  is  covered  by  the 
transparent  conjunctiva.  Its  posterior  surface  by  the  serous 
membrane  of  the  aqueous  chamber.  The  sclerotic  must 
now  be  separated  from  the  choroid  or  middle  coat  by  laying 
the  eyeball  on  a  flat  surface,  and  cutting  through  the  most 
elevated  portion  of  sclerotic  with  scissors,  when  the  choroid, 
which  was  separated  by  the  weight  of  its  contents  will  be 
exposed.  It  is  connected  to  the  sclerotic  by  vessels  and 
nerves  which  form  membrana  fusca,  distinguishable  as  a 
few  dark  thread-like  fibres  running  from  one  to  the  other. 
The  choroid  is  a  dark  brown  membrane,  on  the  surface  of 
which  we  see  a  number  of  light  blue  thread-like  vessels 
ramifying,  forming  the  external  layer  of  the  choroid  (venm 
vorticoscE,  so  called  from  a  fancied  resemblance  to  a  whirl- 
pool) .  The  next  layer  mainly  consists  of  arteries  arranged 
in  festoons,  of  which  the  convexities  are  anteriorly  situated, 
tunica  Uuyschiana.  It  rests  upon  a  layer  of  polygonal  pig- 
ment cells,  which  constitutes  the  pigmentary  layer,  and  in 
which  the  rods  and  cones  which  form  the  external  layer  of 
the  retina,  are  imbedded.  Towards  the  anterior  part  of 
the  sclerotic  the  choroid  becomes  reflected  into  the  cavity 
of  the  eyeball,  to  form  the  "setting"  for  the  crystalline 
lens  ;  and,  as  the  diameter  of  the  lens  is  less  than  that  of 
the  chamber  at  this  part,  the  choroid  becomes  puckered  to 
accommodate  it  to  the  size  of  the  parts.  The  puckerings 
are  ciliary  processes,  the  outer  margin  of  which  is  termed 
the  ora  serrata.  The  inner  margin  comes  in  contact  with 
the  capsule  of  the  lens  to  which  it  is  attached,  and  between 
the  two  is  situated  a  triangular  canal,  the  canal  of  Petit. 
(Some  uncertainty  seems  to  exist  as  to  the  situation  of  this 
canal.  I  have  followed  Huxley.)  The  ciliary  processes 
also  contain  some  muscular  fibres ;  anteriorly  they  are 
covered  by  the  lining  membrane  of  the  aqueous  chamber, 
posteriorly  by  the  retina.  They  are  continuous  with  the 
uvea,  a  layer  of  pigmentary  matter  which  covers  the  pos- 


148  OUTLINES    OF   EQUINE   ANATOMY. 

terior  surface  of  tlie  iris,  and   gives  tlie   eye  its  colour 
(deficiency  of  this  constitutes  "  wall  eyes  ").     The 

Iris  is  a  muscular  diaphragm,  which  projects  into  the 
cavity  of  the  eyeball,  leaving  centrally  an  oblong  opening, 
the  pupillary  opening  or  pupil.     It  consists  of  two  orders 
of  unstriated  muscular  fibres : — circular,  surrounding  the 
pupil,  and  which  cause  it  to  contract;  radiating,  which 
extend  from  the  outer  circumferent  margin  to  the  pupil, 
which  they  serve  to  enlarge.    These  are  posteriorly  covered 
by  the  uvea,  which  overhangs  the  pupil  above  and  below, 
forming  dark  pigmentary  masses  visible  in  the  living  sub- 
ject, corpora  nigra.     They  are  largest  at  the  upper  margin 
of  the    pupil,  and    frequently  are  wanting    below.      The 
anterior  and  posterior  surfaces  of  the  iris  are  covered  by 
serous  membrane  continuous    around  the  margin  of   the 
pupil.     The  outer  margin  of  the  iris  is  attached  to  the 
ciliary  ligament,  a  structure  containing  unstriated  mus- 
cular fibre,  situated  at  the  outer  circumferent  margin  of 
the  posterior  surface  of  the  cornea,  and  serving  to  connect 
together  the  cornea,  sclerotic,  iris,  ciliary  processes,  and 
choroid  ;  in  its  substance  is  the  canal  of  Fontana.     The 
optic  nerve  runs  from  the  optic  decussation  at  the  base  of 
the  brain,  through  foramen   optici,  after  emerging  from 
which  it  is  pierced  by  arteria  centralis  retinae,  a  branch  of 
the  ophthalmic.     It  runs  through  the  orbit  with  this  artery 
in  its  centre,  and  invested  by  a  stout  sheath,  which  extends 
from  the  dura  mater  to  the  sclerotic.     After  piercing  the 
lamina  cribrosa,  its  fibres  radiate  on  the  inner  surface  of 
the  choroid,  forming  the  middle  layer  of  the  retina,  or 
tunica  nervosa,  which  extends  as  far  as  the  outer  margin 
of  the  ciliary  processes,  ora  serrata.     On  its  external  sur- 
face it  has  the  tunica  Jacobi  or  bacillary  layer,  which  con- 
sists of  nerve-cells  (rods,  cones,  and  ganglion  cells)  imbedded 
in  the  pigmentary  layer  of  the  choroid.     On  its  internal 
surface  are  blood-vessels,  which  in  the  living  subject  may 
be  seen  by  means  of  the  ophthalmoscope  (tunica  vasculosa) . 
At  the  opening  of  the  optic  nerve  into  the  eye,  optic  disc  or 
blind  spot,  visible  on  careful  inspection  of  the  living  sub- 
ject, nerve-cells  are  deficient,   while   there  is    a   prepon- 
derance of  nerve-fibres.     In  the  human  subject  the  macula 
lutea  or  foramen  of  Soemering  presents  exactly  opposite 
conditions,  nerve-cells  being   here   most  numerous.      We 
have  failed  to  distinguish  it  in  the  horse.     The  different 


SPtClAL    ANATOMY.  149 

layers  of  the  retina  are  connected  together  by  areolar  tissue, 
which  is  continued  over  the  posterior  surface  of  the  ciliary 
processes,  forming  the  zona  ciliaris  or  zone  of  Zinn,  which 
extends  as  far  as  the  capsule  of  the  lens.  At  the  inner 
and  upper  part  of  the  choroid  we  distinguish  a  part  pre- 
senting a  peculiar  greenish  metallic  lustre,  tapetum 
lucidum,  which  by  reflecting  instead  of  absorbing  the  rays 
of  light,  enables  the  animal  to  "  see  in  the  darJc.'' 

The  chambers  of  the  eye  are  three  in  number.  The 
anterior  chamber  is  situated  between  the  cornea  and  the 
iris.  It  communicates  with  the  posterior  chamber,  which  is 
between  the  iris,  ciliary  processes,  and  the  capsule  of  the 
lens,  through  the  pupillary  opening  (this  communication 
seems  to  be  closed  in  the  foetus  by  a  vascular  membrane, 
memhrana  pupillarisy  which,  however,  is  merely  the  vascular 
anterior  part  of  the  capsule  of  the  lens  to  which  the  iris  is 
attached).  These  two  chambers  are  lined  by  the  mem- 
brane of  Demeurs  or  Descemet,  which,  therefore,  covers  the 
posterior  surface  of  the  cornea,  invests  both  surfaces  of 
the  iris,  and  is  continued  over  the  anterior  surface  of  the 
ciliary  processes  and  the  capsule  of  the  lens.  It  secretes  the 
aqueous  humour,  a  fluid  consisting  of  water  and  a  small 
quantity  of  saline  matter  and  albumen  dissolved  in  it.  It 
serves  to  afford  free  play  to  the  iris,  to  preserve  the  due 
convexity  of  the  cornea,  and  to  (slightly)  influence  the 
direction  of  the  rays  of  light. 

The  dark  chamber  is  the  largest  of  the  three,  anteriorly 
bounded  by  the  capsule  of  the  lens,  m  all  other  parts  it  is 
circumscribed  by  the  retina.  The  membrane  lining  it,  the 
hyaloid  membrane,  also  sends  trabeculse  inwards,  by  which 
the  cavity  is  divided  into  numerous  cells,  in  which  we  find 
a  fluid  analogous  to  the  aqueous  humour,  but  which  in 
consequence  of  this  arrangement  does  not  flow  freely  when 
the  dark  chamber  is  punctured ;  this  is  the  vitreous  humour, 
through  its  centre  in  the  foetus,  from  behind  forwards  to 
the  lens  runs  a  branch  of  arteria  centralis  retinae.  Between 
the  aqueous  and  vitreous  humours  is  situated  the  crystal- 
line lens  (or  third  humour  of  the  eye) .  It  is  enclosed  in 
a  capsule,  the  outer  circumferent  margin  of  which  is 
attached  to  the  free  extremity  of  the  ciliary  processes  and 
of  the  zone  of  Zinn.  Its  anterior  surface  is  covered  by  the 
membrane  of  Demeurs,  its  posterior  by  the  hyaloid  mem- 
brane, and  the  connective  continuation  of   the  retina  is 


150  OUTLINES   OF   EQUINE   ANATOMY. 

attached  along  its  margin.  The  lens  itself  is  biconvex, 
being  most  convex  posteriorly.  It  is  composed  of  numerous 
concentric  transparent  layers,  which  increase  in  density 
from  without  inwards.  In  the  centre  is  a  circular  nodule, 
consisting  of  three  triangular  portions.  The  lamince  con- 
sist of  fibres  denticulated  at  their  margins  and  decreasing 
in  size  towards  each  extremity.  By  apposition  of  their 
denticulse  they  form  firm  continuous  layers,  of  which  the 
external  is  liquid,  and  serves  to  allow  movement  of  the 
lens  in  its  capsule ;  it  is  termed  the  liquor  Morgagni,  but 
its  liquidity  is  supposed  to  be  the  result  of  post-mortem 
change. 

The  ciliary  arteries  and  arteria  centralis  retince  supply 
the  eyeball  with  blood ;  the  ciliary  nerves  endow  it  with 
ordinary  sensation ;  the  (yptic  nerve  with  the  special  sense 
of  sight. 

The  first  trace  of  the  embryo  mammal  is  a  longitudinal 
layer  of  cells,  and  from  this  both  above  and  below  an 
arch  is  formed.  The  inferior  or  hcemal  arch  is  mainly 
composed  of  soft  structures  which  are  supported  by  a 
bony  framework ;  it  forms  the  face,  thorax  and  abdomen. 
The  superior  or  neural  arch  subsequently  becomes  a  bony 
canal  formed  of  many  segments  connected  together  by 
various  structures,  which  posteriorly  comes  to  a  point, 
anteriorly  four  of  its  segments,  or  vertebrae  form  a  large 
ovoid  cavity  with  continuous  walls,  the  CRANIUM,  Twelve- 
bones  combine  to  form  the  cranium,  four  pairs  and  four 
single  bones  : — 

Frontal,  parietal,  squamous  and  petrous  temporal  lx)nes. 
(Pairs.) 

Occipital,  ethmoid,  sphenoid,  and  os  triquatrum. 
(Single.) 

These  bones  are  for  the  most  part  formed  of  tY*-o  dense 
layers  between  which  is  cancellated  structure.  The  central 
portion  contains  large  veins,  and  is  termed  the  diploe, 
the  compact  laminae  are  the  vitreous  tables.  The  imsterior 
'j)art  of  the  cranium  is  formed  by  the  occiput  through  the 
centre  of  which  the  foramen  magnum  passes.  Inferiorly 
on  either  side  of  this  is  a  foramen  condyloideum.  The 
roof  of  the  cavity  is  formed  posteriorly  by  the  occiput 
which  is  united  anteriorly  to  os  triquatrum  (centrally) 
and  to  the  parietal  bones  on  either  side.  The  latter  also 
help  to  form  the   lateral  ivalls  of  the  cavity.     Anteriorly 


SPECIAL   ANATOMY.  151 

tlie  roof  is  formed  by  the  frontal  bones  from  whicli  a 
plate  projects  downwards  to  tbe  upper  extremity  of  the 
crista  galli  process  of  tbe  ethmoid  bone,  which  forms  the 
centre  of  the  anterior  surface  and  on  either  side  of  which 
are  found  the  ethmoidal  fossae  (or  olfactory  sinuses) 
which  are  bounded  by  the  cribriform  'plate  of  the  ethmoid, 
while  the  body  of  the  ethmoid  forms  the  lower  part  of 
the  anterior  surface.  In  forming  the  lateral  part  of  the 
walls  of  the  cranium  the  parietal  bones  articulate  with  the 
wing  of  the  sphenoid  and  with  the  squamous  temporal,  and 
the  latter,  in  its  turn,  is  posteriorly  almost  completely 
separated  by  the  petrous  temporal  bone  from  the  occiput. 
The  floor  of  the  cranium  is  formed  posteriorly  by  the 
basilar  process  of  the  occiput,  from  which  the  body  of  the 
sphenoid  runs  forwards  to  the  body  of  the  ethmoid. 
From,  the  lateral  part  of  the  body  of  the  sphenoid  the 
alae  run  to  articulate  anteriorly  with  the  ethmoid  and 
frontal  bones,  laterally  with  the  parietal  and  squamous 
temporal ;  posteriorly  each  presents  a  rough  margin  with 
several  notches  which  combines  with  the  basilar  process  of 
the  occiput  and  the  temporal  (petrous)  bone  to  form  the 
foramen  lacerum  basis  cranii. 

Foramina  of  the  cranium.  Foramen  magnum,  formed 
wholly  by  the  occiput.  Affords  attachment  to  the  anterior 
margin  of  the  dura  mater  of  the  spinal  cord  and  gives 
passage  to  the  spinal  cord,  which  here  commences  from 
the  medulla  oblongata,  and  its  membranes.  Also  to 
venous  sinuses,  the  meningeal  and  basilar  arteries,  and  the 
major  portion  of  the  spinal  accessory  pair  of  nerves. 
Forameyi  condyloideum,  formed  by  the  occiput  at  the  side 
of  foramen  magnum,  in  front  of  the  condyle.  It  gives 
passage  to  the  twelfth,  lingual,  or  hypoglossal  nerve. 

Foramen  lacerum  basis  cranii,  situated  at  the  side  of  the 
basilar  process  of  the  occiput,  formed  by  the  occipital, 
sphenoid,  and  petrous  temporal  bones.  In  the  human  sub- 
ject by  a  bony  septum  is  divided  into  two  parts  (in  the 
horse  by  a  ligament)  ;  through  the  posterior  run  the  glosso- 
pharyngeal, pneumogastric,  and  spinal  accessory  nerves ; 
through  the  anterior,  the  inferior  maxillary  division  of  the 
fifth,  internal  carotid  artery,  and  meningeal  branches,  and 
a  dilated  vein  running  from  the  cavernous  sinus  to  the 
jugular  at  its  commencement. 

Foramen  auditorium  internum.     A  circular  opening  at 


153  OUTLINES    OE    EQUINE    ANATOMY. 

^"he  centre  of  tlie  cranial  surface  of  the  petrous  temporal 
bone.  It  gives  passage  to  the  seventh  and  eighth  nerves, 
aad  runs  to  the  internal  ear  though  it  gives  off  a  portion 
which  passes  to  the  middle  ear.  On  the  upper  surface  of  the 
body  of  the  sphenoid,  laterally  are  broad  channels  through 
which  the  superior  maxillary  division  of  the  fifth  runs,  and 
thus  gains  the  foramen  rotundum,  which,  in  proceeding  to 
the  bottom  of  the  orbit,  unites  with  the  sub-spherioidal  fora- 
men, which  passes  through  the  wing  of  os  sphenoides,  and 
which  gives  passage  to  the  internal  maxillary  artery.  Thus 
through  the  anterior  part  of  the  foramen  rotundum,  the 
superior  maxillary  division  of  the  fifth  nerve  and  the  in- 
ternal maxillary  artery  pass.  Just  above  this  and  situated 
between  the  ethmoid  and  the  sphenoid  bones  is  foramen 
lacerum  orhitale,  through  which  the  third,  fourth,  ophthalmic 
division  of  the  fifth  and  sixth  nerves,  and  the  ophthalmic 
artery  and  vein  run  (the  ophthalmic  vein  connects  the 
superior  varicose  vein  of  the  face  with  the  cavernous  sinus). 
In  front  of  the  sella  turcica  or  upper  surface  of  the  body 
of  the  sphenoid,  there  are  two  foramina  running  forwards 
through  the  ethmoid  bone  connected  anteriorly  by  a  space 
which  is  covered  by  the  inferior  extremity  of  the  cristagalli 
process  and  in  which  the  optic  decussation  rests.  These 
are  the  foramina  optici.  They  give  passage  to  the  optic 
nerves  covered  by  their  dense  sheath  of  dura  mater,  and 
open  into  the  lower  part  of  the  orbits  by  a  common  opening, 
which  they  share  with  the  foramina  lacera  orbitale,  and 
rotunda.  This  is  the  sphenoideal  hiatus,  just  above  its 
superior  rough  margin  is  forame7ipathetici,  which  only  gives 
passage  to  a  few  small  vessels.  Internally  situated  is  fora- 
men orhitale  internum,  which  passes  to  the  outer  lateral 
part  of  the  ethmoidal  fossa,  thus  passing  directly  into  the 
cranial  cavity.  Through  it  the  lateral  nasal  artery  and 
vein  run.  Numerous  other  foramina  are  found  passing 
through  the  cranial  walls,  but  are  unnamed  ;  through  them 
pass  vessels  and  nerve-fibres.  Some  others  are  generally 
enumerated  as  cranial  foramina,  though  they  do  not  pass 
into  the  cranial  cavity.  Foramen  auditorium  externum 
runs  through  the  external  auditory  process,  and  at  the 
middle  ear,  in  the  recent  subject,  presents  the  membrana 
tympani.  It  is  lined  by  common  integument.  Foramen  styloi- 
deum  is  that  opening  through  which  the  facial  nerve  emerges 
from  the  middle  ear ;  it  is  divided  into  two  parts ;  from 


SPECIAL   ANATOMY.  153 

the  superior  tlie  nerve  emerges,  througli  the  inferior  the 
Eustachian  tube  communicates  with  the  middle  ear.  It  is 
just  at  the  root  of  the  styloid  process  of  the  petrous  tem- 
poral bone.  The  inner  surface  of  the  os  triquatrum 
presents  an  eminence  (ossific  tentorium)  consisting  of  the 
convergence  of  three  irregular  bony  ridges  from  which 
prominences  run.  On  either  side  of  the  wall  of  the  cavity 
one  runs  to  the  floor  of  the  cranium,  and  one  runs  forwards 
along  the  central  line  to  the  crista  galli  process.  In  other 
parts  the  roof  and  sides  of  the  cranium  present  slight  pro- 
minences which  separate  broad  shallow  depressions  (digital 
imjpressions)  which  are  adapted  to  the  convolutions  of  the 
brain. 

The  brain  is  covered  by  three  membranes — dura  mater, 
arachnoid,  and  pia  mater.  The  dura  mater  is  externally 
placed,  and  is  a  dense  fibrous  membrane,  which  forms  the 
internal  periosteum  of  the  skull.  It  presents  processes, 
some  of  which  run  outwards,  others  inwards.  Those  pass- 
ing outwards  establish  its  connection  with  the  periosteum 
of  the  outer  surface  of  the  bones  by  passing  through  the 
immovable  joints  between  them  ;  this  accounts  for  the 
difficulty  experienced  in  separation  of  the  dura  mater  from 
the  bones  at  the  sutures.  The  processes  running  inwards 
are  two  in  number.  Falx  cerebri  is  a  sickle-shaped  fold, 
running  from  the  superior  extremity  of  the  crista  galli, 
and  increasing  in  size  until  it  terminates  posteriorly  in 
becoming  attached  to  the  ossific  tentorium.  It  is  broadest 
above  and  grows  narrow  below,  forming  a  sharp  edge.  It 
fits  into  the  superior  longitudinal  fissure  of  the  brain. 
Along  its  attached  margin  runs  the  superior  longitudinal 
sinus,  along  its  free  margin  the  inferior  longitudinal  sinus. 
These  are  connected  together  posteriorly  by  the  straight 
sinus,  into  the  anterior  part  of  which  vena  Galeni  empties 
itself,  after  running  from  the  velum  interpositum  and  from 
the  upper  surface  of  the  corpus  callosum.  These  sinuses  are 
dilated  veins  situated  in  the  dura  mater,  which  splits  to 
accommodate  them.  They  are  lined  by  epithelium  con- 
tinuous with  that  of  the  other  veins,  and  at  various  parts 
we  see  fibrous  cords  (cordce  Willissii),  which  run  across 
them  to  prevent  undue  distension.  From  the  lateral  parts 
of  the  ossific  tentorium  run  folds  to  the  floor  of  the 
cranium,  the  tentorial  membrane.  They  are  attached  to 
the  inner  ridges  of  the  parietal  bones,  and  project  into  the 


154  OUTLINES    OF    EQUINE   ANATOMY. 

great  transverse  fissure,  in  which  thej  terminate  in  a  sharp 
edge.  In  their  substance  run  the  lateral  sinuses  from  the 
torcular  HeropMli  above  to  the  cavernous  sinus.  The  fifth 
nerve  (sensory  portion)  passes  into  them  about  their 
centre,  and  they  thus  contain  it  with  its  gasserian  ganglion. 
The  torcular  Herophili,  therefore,  is  a  venous  sinus,  situated 
against  the  ossific  tentorium,  which  receives  the  straight 
(and  superior  longitudinal)  sinuses,  and  from  which  the 
lateral  sinuses  and  also  the  occipital  sinuses  run.  The 
latter  pass  backwards  over  the  roof  of  the  cerebellal  cavity. 
Between  the  fifth  nerves,  at  the  base  of  the  brain,  the  layers 
of  the  dura  mater  separate,  forming  the  cavernous  sinus,  and 
imbedding  a  peculiar  reddish-black  body,  circular,  and 
flattened  from  above  downwards,  the  use  of  which  is  un- 
known, but  which  receives  the  inferior  extremity  of  the 
tuber  cinereum — the  pituitary  body.  Around  the  posterior 
and  lateral  parts  of  this  body  is  situated  the  cavernous  sinus 
lined  by  epithelium,  to  which  run  the  lateral  sinuses  supe- 
riorly, the  anterior  petrosal  anteriorly,  and  the  posterior 
petrosal  posteriorly,  from  the  floor  of  the  cranium ;  the 
latter  blend  with  the  sinuses  of  the  floor  of  the  spinal  canal 
posteriorly.  It  also  receives  anteriorly  the  posterior  ex- 
tremity of  the  superior  varicose  vein  of  the  face,  which 
passes  through  foramen  lacerum  orbitale.  Inferiorly  it 
sends  off  prolongations,  which  pass  through  foramen 
lacerum  basis  cranii,  and  from  which  the  jugular  veins 
commence.  In  the  cavernous  sinus  run  the  internal 
carotid  arteries,  covered  by  reflections  of  the  epithelial 
lining  layer  ;  they  pass  from  foramen  lacerum  basis  cranii, 
communicating  by  a  transverse  branch  behind  the  pituitary 
body,  and  emerging  from  the  dura  mater  at  the  base  of  the 
brain,  opposite  the  commencement  of  the  fissure  of  Sylvius. 
The  dura  mater  of  the  brain  is  continuous  with  that  of  the 
cord  through  the  medium  of  its  attachment  to  the  margin 
of  the  foramen  magnum  of  the  occiput.  It  is  attached  to 
almost  all  the  foramina  around  their  margins,  and  is  con- 
tinued over  the  optic  nerve  as  far  as  the  sclerotic,  where  it 
terminates  in  forming  the  lamina  cribrosa.  On  the  outer 
surface  of  the  dura  mater,  especially  at  the  attached 
margin  of  the  falx  cerebri,  have  been  distinguished  minute 
nodular  bodies,  largest  in  old  subjects,  glands  of  PaccMoni. 
The  arachnoid  is  a  serous  membrane,  and  presents  a 
parietal  and  a  visceral  portion.     The  parietal  portion  lines 


SPECIAL    ANATOMY.  155 

the  dura  mater  ;  the  visceral  portion  invests  the  pia  mater. 
Between  these  layers  is  a  serous  fluid,  the  arachnoid  fluid  ; 
and  between  it  and  the  pia  mater  is  the  subarachnoid 
fluid.  Posteriorly  this  membrane  forms  the  posterior  part 
of  the  roof  of  the  fourth  ventricle,  arachnoidean  valve;  it 
becomes  reflected  from  the  different  prominences  of  the 
brain,  and  does  not  dip  between  into  the  sulci.  Subarach- 
noid" spaces  are  most  marked  in  front  of  and  behind  the 
optic  decussation  and  below  the  posterior  lobes  of  the 
cerebrum  in  the  transverse  fissure.  The  pia  mater  is  the 
vascular  membrane  of  the  brain,  the  surface  of  which  it 
closely  invests.  It  is  prolonged  into  the  cavities  of  the 
brain  in  several  i^laces  ;  thus,  in  passing  through  the  trans- 
verse fissure,  it  runs  forwards  under  the  posterior  part  of 
the  cerebrum  and  becomes  thicker,  forming  the  velum 
interpositum,  which  is  the  roof  of  the  third  ventricle,  and 
which  anteriorly  bifurcates,  forming  the  plexus  choroides  of 
the  lateral  ventricles,  which,  passing  through  the  foramina  of 
Munro  (anterior  communicating  foramina)  and  between 
the  hippocampi  and  thalami  optici,  extend  into  the  poste- 
rior cornua  of  their  respective  ventricles.  Underneath  the 
posterior  part  of  the  cerebellum  it  is  similarly  reflected 
into  the  fourth  ventricle,  forming  the  plexus  choroides  of 
the  fourth  ventricle. 

The  brain  is  primarily  divided  into  cerebrum,  cerebellum, 
200ns  Varolii,  and  medulla  oblongata.  The  cerebrum  is  the 
largest  part,  and  is  that  ovoid  mass  situated  in  the  ante- 
rior part  of  the  cranium.  It  presents  on  its  external  sur- 
face a  number  of  convolutions,  gijri,  separated  by  grooves, 
sulci,  which  in  the  human  subject  are  capable  of  division 
into  sets,  but  in  the  horse  present  no  regularity,  except 
that  at  the  middle  line  we  may  observe  the  "  marginal 
convolution."  On  each  side  of  the  superior  longitudinal 
fissure,  and  on  opening  the  fissure,  we  may  see  a  "  gyrus 
fornicatus  "  on  each  side  of  the  bottom  of  it.  The  cerebrum 
is  separated  from  the  cerebellum  by  the  great  transverse 
flssure,  which  extends  on  either  side,  and  also  in  a  forward 
direction,  underneath  the  posterior  lobes  of  the  cerebrum, 
where  it  contains  the  vellum  interpositum.  The  cerebrum 
is  divided  into  two  parts,  hemispheres,  by  the  superior  lon- 
gitudinal flssure,  which  runs  forward  from  the  transverse 
fissure  and  anteriorly  extends  downwards,  putting  in  its 
appearance  at  the  anterior  part  of  the  base  of  the  brain ; 


156  OUTLINES    OF    EQUINE    ANATOMY. 

and  anteriorly  and  posteriorly  presents  somewhat  firm  union 
of  the  hemispheres.     It  contains  the  falx  cerebri,  and  is 
terminated  below  by  a  layer  of  white  matter,  corpus  cal- 
losum,  which  connects  the  two  hemispheres,  and  is  com- 
posed of   fibres  which  run  transversely  from  the   white 
substance  of  the  hemispheres,  the  anterior  fibres   being 
curved  forwards,  the  posterior  backwards,  so  that  the  nar- 
rowest portion  is  that  shown  by   separation  of  the  two 
hemispheres  without  incision.     On  its  upper  surface  may 
be  distinguished  a  central   longitudinal   line,  the   rop/ie, 
along  which  arteria  corporis  callosi  passes,   and  on  each 
are  the  linese  longitudinales  laterales,  while  lineae  trans- 
versae  intersect  these  at  right  angles.    The  corpus  callosum 
terminates  both  anteriorly  and  posteriorly  by  a  rounded 
extremity  ;    the  anterior  is  the  genu,  the   posterior   the 
splenu.      From  the  latter  the  fornix  runs  in   a  forward 
direction,  connecting  together  the  hippocampi.    Anteriorly, 
at  the  foramen  of  Munro,  the  fornix  terminates  in  four 
crura.     The  anterior  run  to  the  base  of  the  brain,  where 
they  terminate  in  the  single  corpus  albicans   (there  are 
two  in  the  human  subject).     The  posterior  take  the  name 
of  corpora  fimbriata,  and  extend  into  the  posterior  cornua 
of  the  lateral  ventricle.     The  upper  surface  of  the  fornix 
is  connected  to  the  under  surface  of  the  corpus  callosum 
by  the  septum  lucidum,  a  thin  layer  of  nerve  matter  which 
separates  the  lateral  ventricles  one  from  the  other,  and 
between  the  two  layers  of  which  is  the  fifth  ventricle  (which 
we  have  never  found  in  the  horse).     By  removing  a  small 
layer  from  the  upper  surface  of  the  cerebral  hemispheres 
we  may  demonstrate  that  they  are  composed  externally  of 
grey  matter,  internally  of  white.     The  grey  matter,  cine- 
ritious,  is  of  uniform  thickness  throughout,  but  since  it 
invests  the  convolutions  presents  a  wavy  margin.      The 
white  or  medullarij  matter   in  this  section  is  termed  the 
centrum  ovale  minor,  and  presents  the  cut  extremities  of 
vessels,   through   which,   in    the   fresh   subject,   a    small 
quantity  of  blood  oozes,  puncta  vasculosa.     If  sections  are 
now  made  through  both  hemispheres  on  a  level  with  the 
corpus  callosum,  the  whole  of  the  upper  surface  of  that 
layer   or   ceiitrum   ovale   major   is   exposed.     By   incision 
through  this  on  either  side  we  lay  open  the  cavity  of  the 
lateral  ventricle,  a  space  divisible  into  anterior  and  pos- 
terior  cornua,  bounded  anteriorly  and  externally  by  the 


SPECIAL    ANATOMY.  157 

substance  of  the  hemispheres,  superiorly  by  the  corpus 
callosum,  internally  separated  from  its  fellow  by  the  sep- 
tum lucidum,  in  the  anterior  part  of  which  is  the  foramen 
of  Monro  or  anterior  communicating  foramen.  Its  floor  pre- 
sents the  following  structures  in  order  from  before  back- 
wards : — 

Corpus  striatum,  taenia  semicircularis,  plexus  choroides, 
corpus  fimbriatum,  hippocampus. 

Corpus  striatum  is  a  pear-shaped  body,  the  base  of  which 
lies  against  its  fellow,  separated  by  brain  substance,  the 
apex  extends  into  the  anterior  cornu,  which  runs  down- 
wards, outwards,  and  foi^wards.  Externally  it  is  covered 
by  a  thin  layer  of  white  matter,  but  is  dark  in  colour,  and 
has  a  few  small  vessels  at  its  posterior  margin.  By  passing 
a  pin  through  it  we  shall  find  that  it  is  situated  just  above 
locus  perforatus  anticus  at  the  base  of  the  brain.  It  is 
named  from  its  composition  of  alternate  layers  of  grey 
and  white  matter.  At  its  posterior  margin  is  distinguish- 
able a  thin  layer  of  white  matter,  tcenia  semicircularis, 
which  is  generally  covered  by  the  plexus  choroides  which 
has  been  already  described,  and  which  also  covers  the 
posterior  crus  of  the  fornix,  corpus  fimbriatum,  a  thin 
layer  which  runs  downwards  into  the  posterior  cornu, 
where  it  terminates  in  a  small  enlargement,  pes  accessorius. 
Immediately  behind  it  is  the  hippocampus.  (There  are 
two,  major  and  minor,  in  each  lateral  ventricle  of  man.) 
This  is  an  internal  convolution  of  the  cerebral  hemi- 
spheres, it  rests  upon  the  velum  interpositum  inferiorly, 
and,  with  the  plexus  choroides  and  corpus  fimbriatum  ex- 
tends into  the  posterior  cornu,  where  it  terminates  in  the 
pes  hippocampi. 

The  posterior  cor7iit  runs  backwards,  outwards,  and  down- 
wards, and  then  forwards  and  inwards.  It  is  shaped  like 
a  ram's  horn,  and  its  apex  is  situated  in  the  mastoid  lobule 
at  the  base  of  the  brain.  The  hippocampus  is  separated  by 
the  velum  interpositum  from  the  thalamus  opticus,  a  some- 
what irregular,  rounded  body,  which  constitutes  the  deep 
seated  origin  of  the  optic  nerve.  It  presents  on  its  upper 
surface  three  prominences,  corpora  geniculata  externum  and 
internum,  and  the  tubercle.  The  inner  surface  of  this  body 
is  connected  with  its  fellow  by  the  middle  or  grey  commissure, 
anteriorly  situated  to  which  is  the  foramen  of  Monro  or 
anterior  communicating  foramen,  which  not  only  connects 


158  OUTLINES    OF    EQUINE    ANATOMY. 

the  cavities  of  tlie  lateral  ventricles  but  also  extends  down 
to  the  base  of  the  brain,  where  it  forms  the  cavity  of  the 
tuber  cinereum,  and  the  inf undibulum,  and  extends  as  far  as 
the  pituitary  body.  Anteriorly  it  is  bounded  by  the  anterior 
tvJiite  commissure,  which  connects  the  two  corpora  striata 
together.  Posteriorly  situated  to  the  grey  commissure  is 
the  posterior  commu7iicating  foramen,  which  forms  the  com- 
mencement of  the  iter  a  tertio  ad  quartum  ventriculum. 
Just  above  this  is  a  small  black  cone-shaped  body,  the 
pineal  gland,  the  use  of  which  is  unknown — we  sometimes 
find  it  much  enlarged.  It  contains  pigmentaiy  matter  and 
vessels  arranged  in  an  areolar  stroma,  and  from  it  forwards 
along  the  inner  margins  of  the  thalamic  optici,  above  the 
grey  commissure,  run  the  crura  of  the  pineal  body,  which 
anteriorly  blend  with  the  substance  of  the  thalami.  The 
third  ventricle  is  the  cavity  through  which  the  grey  com- 
missure passes  "  like  a  transverse  beam."  Anteriorly,  it  is 
bounded  by  the  anterior  white  commissure,  superiorly  by 
the  velum  interpositum,  laterally  by  the  thalami  optici 
and  the  crura  of  the  pineal  body.  Inferiorly  by  the  upper 
surface  of  certain  structures  situated  at  the  base  of  the 
brain — tuber  cinereum,  corpus  albicans,  and  locus  perfora- 
tus  posticus.  It  presents  three  openings :  inferiorly,  the 
infundibular ;  sup ero- anteriorly,  the  anterior  communi- 
cating foramen ;  supero-posteriorly,  the  posterior  communi- 
cating foramen.  Its  posterior  boundary  is  the  posterior 
white  commissure,  which  connects  together  the  corpora  qua- 
drigemina,  and  forms  the  roof  of  the  iter  a  tertio  ad  quartum 
ventriculum.  The  corpora  quadrigemina  are  four  bodies 
posteriorly  placed  to  the  pineal  body.  The  anterior  pair  is 
the  roundest,  largest,  and  darkest,  and  is  termed  the  nates, 
the  posterior,  or  testes,  more  ovoid  in  form,  posteriorly  receive 
tracts  of  white  matter  running  from  the  cerebellum,  iter 
e  cerehello  ad  testes.  These  tracts  are  connected  together  by  a 
thin  membraniform  layer  of  matter,  valve  of  Yieussens,  from 
which  the  fourth  pair  of  nerves  arise.  They  circumscribe 
anteriorly  the  fourth  ventricle,  "a  boat-shaped  cavity," 
situated  at  the  upper  part  of  the  medulla  oblongata.  Its 
roof  is  formed  anteriorly  by  the  valve  of  Yieussens,  cen- 
trally by  the  under  surface  of  the  cerebellum,  posteriorly 
by  the  arachnoidean  valve.  Its  floor  and  lateral  walls  are 
formed  by  the  pillars  of  the  medulla  oblongata,  anteriorly 
its  cavity  is  continuous  through  the  aquaduct  of  Sylvius  or 


SPECIAL   ANATOMY.  159 

iter  a  tertio  ad  quarhim  ventriculum  with  the  third  ventricle. 
Its  posterior  part,  frora  its  likeness  to  the  nib  of  a  pen,  is 
termed  calamus  scriptorius,  and  is  continued  through  the 
spinal  cord  by  a  canal  which  extends  centrally  between  its 
columns.     The  cerebellum  is  a  round  body,  situated  in  a 
special  division  of  the  cranium,  posteriorly  to  the  cerebrum 
from  which  it  is  separated  by  the  ossific   and  the  mem- 
branous tentoria ;  and  to  which  it  is  connected  on  each  side 
by  the  iter  e  cerebello  ad  testes.     It  presents,  on  either 
side  of  the  median  line,  running  from  behind  forwards  a 
fissure,  and  thus  the  organ  is  divided  into  three   parts. 
Centrally  is  a  "  caterpillar-shaped  "  body,  the  anterior  part 
of  which  is  the  anterior  vermiform  process;   the  posterior 
part,  the  posterior  vermiform  process,  on  either  side  of  this 
is  a  lobe.    By  an  incision  from  behind  forward  in  the  median 
plane  we  may  expose  the  internal  structure  of  the  organ. 
The  surface  of  the  cerebellum  presents  convolutions  which 
are  divided  into  uniform   parts  by  transverse  secondary 
grooves.      The    grey   matter   which  the   external  surface 
presents,  is  arranged  with  regard  to  the  white  as  the  leaves 
of  a  tree  are  to  the  branches,  so  the  white  matter  inferiorly 
terminates  in  abroad  base.     This  arrangement  is  the  arhor 
vitce,  and  the  base  of  the  stem  is  formed  by  three  tracts  of 
white  matter,  the  crura  of  the  cerebellum.     The  anterior 
is  the  iter  e  cerebello  ad  testis,  the  posterior  is  continuous 
with  the  corpus  restiforme  of  the  medulla  oblongata,  the 
middle  passes  under  the  medulla  oblongata,  joining  with 
its  fellow  to  form  a  transverse  band  at  the  base  of  the 
brain,  the  pons  Varolii;    this  is   the  part  which   serves 
to  connect  together  the  three  other  divisions  of  the  brain. 
It  presents  a  longitudinal  groove  along  its  central  line, 
through  which  the  basilar  artery  passes,  and   on  either 
side  of  which  it  becomes  more  prominent,  for  here  is  a 
collection  of  nerve-cells  in  its  substance  constituting  the 
corpus   dentatum,  the   special   centre  of  the  fifth  pair  of 
nerves  which  arises  from  the  lateral  parts  of  its  under 
surface. 

The  medulla  oblongata  is  but  the  commencement  por- 
tion of  the  spinal  cord,  from  which  it  is  distinguished  by 
its  greater  size,  caused  by  the  presence  of  a  few  extra  nerve 
cells  collected  to  form  the  corpus  olivare.  In  addition  to 
this,  like  the  spinal  cord,  it  presents  three  tracts  of  white 
matter    (externally)    continuous  with  those   of  the  cord 


160  OUTLINES   OF   EQUINE   ANATOMY. 

respectively.  Tlie  corpora  pyramidalia  inferior  are  sepa- 
rated from  each,  other  by  the  inferior  longitudinal  fissure, 
which,  however,  is  slightly  obscured  by  the  decussation  or 
passage  to  the  opposite  side  of  the  medulla  of  the  motor 
fibres  of  the  corpora  restiformia,  the  lateral  tracts  of  the 
medulla  oblongata  continuous  with  those  of  the  spinal  cord. 
These  divide  anteriorly,  one  branch  runs  to  the  cerebellum 
forming  its  posterior  crus,  the  other  passes  forwards  to  the 
cerebrum  and  unites  with  fibres  from  the  pyramids  forming 
the  crura  cerebri.  These  restiform  bodies  are  separated 
from  the  inferior  pyramids  by  the  corpora  olivaria,  small 
round  bodies  which  internally  present  an  irregular  grey 
nodule,  corpus  dentatum.  Their  upper  surface  forms  the 
floor  of  the  fourth  ventricle,  and  on  either  side  superiorly 
is  situated  a  small  corpus  pyramidalium  superior.  The  two 
sides  of  the  medulla  oblongata  are  connected  together  by  a 
commissure  formed  of  grey  and  white  matter. 

The  base  of  the  brain  presents  numerous  and  diverse 
structures.  At  the  anterior  part  centrally  is  the  superior 
longitudinal  fissure,  and  on  either  side  of  this  is  an  olfac- 
tory bulb.  This  is  a  rounded  mass  of  grey  matter  situated 
in  the  olfactory  sinus,  from  which  grey  fibres  run  forwards 
through  foramina,  in  the  cribriform  plates.  This  is 
attached  to  the  under  j^art  of  a  tract  of  white  matter 
which  runs  backwards  and  becomes  narrower,  terminating 
in  two  parts  which  separate  at  an  angle  enclosing  a  trian- 
gular space,  locus  perforatus  anticus,  or  substantia  perforata, 
the  out3r  surface  of  the  corpus  striatum.  These  tracts  of 
matter  contain  a  cavity  lined  by  serous  membrane,  which 
in  some  subjects  is  said  to  have  been  found  continuous 
with  the  lateral  ventricle.  From  the  lateral  parts  of  the 
thalamus  opticus  and  from  the  corpora  quadrigemina 
tracts  of  white  matter  run  round  the  lateral  parts  of  the 
crura  cerebri.  At  the  base  of  the  brain  they  unite,  and 
the  fibres  from  this  union  form  two  nervous  cords,  the  optic 
nerves  which  pass  to  the  eye.  This  is  the  optic  decussa- 
tion, the  fibres  from  one  side  pass— to  the  nerve  of  the 
opposite  side,  to  the  nerve  of  the  same  side,  to  the  other 
optic  tract ;  fibres  also  run  from  one  optic  nerve  to  the 
other.  From  the  postero-lateral  parts  of  the  optic  decus- 
sation the  crura  cerebri  run  to  the  anterior  margin  of  the 
pons  Varolii.  They  are  broad  bands  of  white  matter,  and 
from  their  under  surface  the  third  pair  of  nerves,  motores 


SPECIAL    ANATOMY.  161 

oculorum,  arises.     Between  these,   anteriorly  is  the   tuhcrr 
cinereum,  which  is  continued  to  the  pituitary  body  as  the 
infiindibulum,  and  through  which  a  canal  runs.     Imme- 
diately behind  this  is  the  corims  albicans,  formed  by  the 
anterior  crura  of  the  fornix,  and  more  ^posteriorly,  between 
the  crura  cerebri  in  the  human  subject,  is  locus  jjerforatus' 
jposticus,  ivJiicli  in  the  horse  is  represented  merely  by  a  groove^ 
The  hemispheres  of  the  cerebrum  of  man  are  divided  into 
anterior,  posterior,  and  middle  lobes.     At  the  lateral  part 
of  the  crura  cerebri  of  the  horse  is  a  smooth,  round  mass, 
mastoid  lobule   (analogous  to  the  middle  lobe  of  man). 
From  the  optic  decussation  in  front  of  this  the  fissure  of 
Sylvius  runs  outwards,  tending  to  divide  the  hemisphere 
into  an  anterior  and  a  posterior  lobe.     Before  running  over 
the  under  surface  of  pons  Varolii  the  basilar  artery  gives 
off  the  anterior,  posterior,  and  middle  cerebellal  arteries,  after 
doing  so  it  terminates  in  receiving  the  two  posterior  com- 
municating arteries.     These  give  off  the  posterior  cerebral 
arteries    (which   run    upwards   winding   round   the   crura 
cerebri)  and  are  given  off  with  the  anterior  communicating 
and  middle   cerebral  by  the  internal  carotid  after  it  has 
pierced  the  dura  mater.    The  anterior  communicating  artery 
runs  inwards  and  blends  with  its  fellow  in  front  of  the 
optic   decussation.      The   middle    cerebral   runs   outwards 
through  the  fissure  of  Sylvius.    From  the  anterior  commu- 
nicating or  from  the  middle  cerebral  the  ophthalmic  arteries 
pass  through  the  foramina  lacera  orbitale  to  the  orbit,  and 
from    the    centre     of    the    anterior    communicating    the 
anterior  cerebral  artery    (double   in   the   human   subject) 
passes  around  the  anterior  extremity  of  the  corpus  callosum 
into  the  superior  longitudinal  fissure,  where  it  terminates 
in  forming  the  arteria  corporis  callosi.     Thus  we  have  the 
circle  of  Willis  at  the  base  of  the  brain  formed  anteriorly  by 
the  anterior  communicating,  laterally  and  posteriorly  by  the 
posterior  communicating  arteries ;  it  encloses  the  optic  decus- 
sation, tuber  cinereum,  infundibulum,  corpus  albicans,  locu& 
perforatus,  and  part  of  the  crura  cerebri,  and  surrounds  the 
pituitary  body.     We  have  always  found  the  origin  of  the 
third  pair  of  nerves  externally  placed  to  it.     Posteriorly  at 
the  base  of  the  brain  we  see  the  pons  Varolii  running  trans- 
versely, and  a  fifth  nerve  arising  at  either  end  of  it.     Fromj 
the  under  surface  of  the  medulla  oblongata,  just  behind 
the  pons,  on  either  side  of  the  inferior  longitudinal  fissure, 

11 


162  OUTLINES    OF   EQUINE   ANATOMY. 

a  sixth  or  cibducens  nerve  arises  ;  and  more  outwards  and 
posteriorly  placed  the  glosso-2)haryngeal,  pneumogastric, 
spinal  accessory,  and  lingual  nerves,  while  the  seventh  and 
eighth  together  arise  immediately  behind  the  fifth  from  the 
lateral  i^art  of  the  medulla.  The  eleventh  or  spinal 
accessory  nerve  arises  from  the  lateral  part  of  the  spinal 
cord  as  low  down  as  the  fifth  cervical  vertebrae.  It  runs 
towards  the  cranium,  passing  between  the  sensory  and 
motor  roots  of  the  s^^inal  nerves,  receiving  fibres  from  the 
•lateral  part  of  the  cord.  Its  last  fibres  arise  from  the 
medulla  oblongata,  it  then  emerges  from  the  cranium 
through  the  posterior  part  of  foramen  lacerum  basis  cranii, 
and  runs  to  supply  sterno-maxillaris,  levator  humeri  and 
other  muscles  of  the  neck.  It  has  extensive  communica- 
tion with  the  nerves  near  its  origin  and  with  the  superior 
cervical  ganglion.  The  lingual  nerve  passes  between  it  and 
the  glosso-pharyngeal. 

In  laying  open  the  cranium  to  examine  its  contents 
remove  all  surrounding  soft  structures.  Saw  through 
the  forehead  transversely  about  three  quarters  of  an 
inch  above  the  orbital  process  of  the  frontal  bone. 
From  the  extremity  of  this  incision  divide  the  bones 
on  either  side  so  as  to  remove  the  superior  third  of  the 
foramen  magnum  of  the  occiput.  Eaise  the  separated 
portion,  calvarinm,  with  the  chisel,  the  dura  mater  with  its 
falx  cerebri  will  be  seen  attached  to  its  internal  surface. 
The  anterior  part  of  the  spinal  cord  having  been  now  cut 
through,  the  brain  may  be  raised,  and  the  nerves  passing 
from  its  base  divided  in  turn  from  behind  forward.  The 
olfactory  bulbs  will  gener^ally  remain  in  situ.  The  contents 
of  the  cranium  is  termed  the  encephalon. 

The  internal  and  middle  ear  may  be  examined  by  im- 
mersing the  petrous  temporal  bone  in  a  solution  of  hydro- 
chloric acid,  three  drachms  of  the  acid  to  a  c[uart  of  water. 
(We  have  never  tested  this  process  practically,  but  have  seen 
it  recommended.)  After  a  time  the  bone  will  become  dej^rived 
of  earthy  matter  so  that  it  can  be  divided  by  a  common  scal- 
pel. The  foramina  should  be  first  stopped  with  w^ax,  that  the 
©ssicula  auditus  may  remain  uninjured.  The  petrous  temporal 
lone  is  the  hardest  bone  in  the  body ;  it  is,  therefore,  well 
calculated  for  communication  of  the  vibrations  of  the 
atmosphere.  In  it  is  situated  the  organ  of  hearing,  which, 
like  all  other  organs  of  special  sense,  has  certain  nerve-cells 


SPECIAL   ANATOMY.  163 

to  wliicli  tlie  fibres  of  tlie  nerve  of  that  special  sense 
run,  and  a  special  arrangement  whereby  those  influences 
which  cause  the  impressions  are  best  able  to  alter  the 
condition  of  the  cells.  The  ear  is  divided  into  external, 
middle,  and  internal  ears.  The  first  has  been  already 
noticed ;  the  internal  ear  is  that  part  in  which  are  situated 
the  cells  of  hearing.  It  is  divided  into  cochlea,  vestibule, 
and  semicircular  canals.  The  vestibule  is  the  central 
cavity.  It  has  seven  openings  into  it,  those  from  the 
semicircular  canals,  one  from  the  scala  vestibuli  of  the 
cochlea,  and  one  from  the  middle  ear,  fenestra  ovalis.  It 
contains  a  membranous  sac,  the  membranous  vestibule, 
which  is  divided  into  two  parts.  The  superior,  utriculus, 
receives  the  openings  of  the  membranous  semicircular 
canals.  It  is  separated  by  a  membranous  partition  from 
the  inferior  or  sacculus,  which  has  no  openings.  This 
membranous  portion  is  in  contact  both  externally  and  in- 
ternally with  a  serous  fluid.  That  surrounding  it  is  the 
]}erihjmpli,  that  contained  inside  of  it  is  the  enclolymph  and 
contains  numerous  minute  calcareous  particles,  otoconites 
or  otolithes.  The  membranous  semicircular  canals  ex- 
actly resemble  the  bony  cavities  in  which  they  are  placed. 
They  contain  endolymph  and  are  surrounded  by  perilymph. 
They  are  three  in  number,  superior,  internal,  and  p>osterior, 
and  each  canal  opens  by  its  two  extremities  into  the  ves- 
tibule, one  of  these  extremities  is  dilated  to  form  the 
ampulla.  The  undilated  extremities  of  the  superior  and 
internal  canals  open  by  a  common  orifice  into  the  vestibule. 
To  the  ampullae  run  bi'anches  of  the  eighth  or  auditory 
nerve. 

The  cochlea  is  a  cavity  hollowed  out  in  the  substance  of  the 
j)etrouS  temporal  bone,  shaped  like  a  snail's  shell,  consisting 
of  a  canal  arranged  in  a  spinal  manner  around  a  central  bony 
tube,  modiolus.  This  canal  is  largest  at  its  commence- 
ment, and  superiorly  comes  to  a  point.  It  is  divided  into  two 
parts  by  a  spiral  plate,  which  is  internally  attached  to  the 
modiolus  and  projects  into  the  canal.  The  division  is  com- 
pleted by  a  membrane  consisting  of  two  layers  between 
Tvhich  is  the  scala  media  of  the  cochlea.  The  two  portions 
of  the  canal,  termed  respectively  superior  or  scala  vestibuli, 
inferior  or  scala  tympani,  communicate  superiorly.  The 
former  inferiorly  terminates  in  the  vestibule,  the  latter  at 
the  fenestra  rotunda,  an  opening  in  the  bone  closed  by  a 


164  OUTLINES    or    EQUINE    ANATOMY. 

double  fold  of  membrane,  wliicL  serves  to  bring  about  a  com- 
munication between  the  cavities  of  the  cochlea  and  of  the 
tympanum.  On  the  bony  plate  which  separates  the  scalce 
(lamina  sjnralis)  the  fibres  of  the  auditory  nerve  are  spread 
out ;  they  terminate  in  cells  which  are  situated  in  the  scala 
media  (fibres  or  rods  of  Corti),  "  arranged  like  the  key- 
board of  a  piano."  On  reaching  the  internal  ear,  after  pass- 
ing through  foramen  auditorium  internum,  the  auditory, 
portio  mollis,  or  eighth  pair  of  nerves  breaks  up  into  three 
parts.  One  runs  to  the  ampullae,  another  to  the  membranous 
vestibule,  the  third  passing  into  the  modiolus  gives  ofP 
fibres  outward  into  the  lamina  spiralis.  The  intensity  of 
a  sound  is  supposed  to  be  distinguished  in  the  vestibule, 
its  "  tone  "  in  the  scala  media  of  the  cochlea.  The  ves- 
tibule is  connected  with  the  cavity  of  the  tympanum  by 
the  fenestra  ovalis,  which  in  the  fresh  subject  is  closed  by 
mucous  membrane  and  by  the  base  of  the  stapes.  It  will 
be  observed  that  the  cochlea  only  of  the  bony  labyrinth  has 
its  membranous  counterpart  attached  to  the  bony  walls,  the 
membranous  semicircular  canals  and  vestibule  being  sepa- 
rated from  the  bone  by  perilymph. 

The  middle  ear  or  tympanic  cavity  is  situated  between 
the  external  and  internal  ears.  Its  outer  wall  presents  the 
membrana  tymimm,  which  closes  the  foramen  auditorium 
externum.  By  the  foramen  styloideum  it  is  connected 
■with  the  pharynx  through  the  medium  of  the  Eustachian 
tube.  It  communicates  inferiorly  wdth  certain  cavities  in 
the  petrous  temporal  bone  (similar  to  the  sinuses  of  the 
face)  the  mastoid  cells.  Through  this  cavity  the  seventh 
nerve  passes  ;  it  enters  through  foramen  auditorium  in- 
ternum, and  during  its  passage  gives  off  the  chorda  tym- 
pani,  which  runs  to  the  gustatory  branch  of  the  inferior 
maxillary  division  of  the  fifth,  and  also  branches  to  the 
muscles  of  the  middle  ear  ;  then  it  emerges  by  passing 
through  foramen  styloideum.  The  inner  wall  of  the  middle 
ear  presents  two  foramina — fenestra  rotunda,  leading  to  the 
scala  tympani ;  fenestra  ovalis,  leading  to  the  vestibule. 
Into  the  latter  fits  the  base  of  the  stapes,  one  of  a  chain  of 
bones  which  extends  across  the  tympanic  cavity  to  the 
membrana  tympani.  This  bone  is  "  stirrup  shaped,"  and 
its  arch  superiorly  is  connected  by  fibro- cartilage  with  a 
portion  of  the  incus.  In  this  joint  an  osseous  nodule  may 
be  observed,  os  orbiculare,  commonly  enumerated  as  "  th& 


SPECIAL    A-NxVrOMY.  165 

^smallest  hone  in  the  body.''     The  incus  resembles  in  shape  a 
human  molar,  one  of  the  fangs  of  which  articulates  with  os 
orbiculare  ;  the  other  becomes  attached  to  the  bony  wall  of 
the  cavity.    The  crown  has  a  synovial  articulation  with  the 
upper  portion  of  head  of  the  malleus,  the  handle  of  which 
is  attached  to  the  inner  surface  of    membrana  tympani, 
vibrations  of  which  are  thus  communicated  to  the  bony 
chain,  which,  by  the  mechanical  arrangement  of  its  com- 
ponent ossicles,  communicates  them  in  an  increased  degree 
of   intensity   to    the    liquid   contents    of    the    vestibule, 
which    produces    impressions     upon    the    auditory  cells, 
made  more  powerful  by  the  presence  of  the  solid  particles, 
otoconites,  in  the  liquid.     The  bones  of  the  middle  ear  are 
acted  upon  by  muscles,  of  which  we  will  only  particularise 
the  stapedius,  running  from  the  wall  of  the  cavity  to  the 
stapes  at  its  attachment  to  os  orbiculare  and  tensor  tympanij 
running  from  the  margin  of  the  bony  ring  surrounding  the 
tympanum  to  the  handle  of  the  malleus  at  its  attachment 
to  the  membrana.     The  middle  ear  is  lined  by  transparent 
and  thin  mucous  membrane,  which  covers  all  the  structures 
contained  in  it,  and  is  continued  into  the  mastoid  cells. 
It  closes  the  foramen  auditorium  externum  in  forming  the 
inner  lining  of    membrana    tympani,   and   also   fenestrae 
rotunda  and  ovalis.     It  is  continuous  through  the  Eusta- 
<;hian  tube  with  that  lining  the  guttural  pouch  and  the 
pharynx.     The  internal  and  middle  ear  are  supplied  with 
blood  by   the  styloid  division  of  the  posterior  auricular 
branch  of  the  external  carotid ;  they  receive  sympathetic 
fibres  from  the  otic  ganglion,  a  small  collection  of  nerve- 
<iells  situate'l  on  the  inner  surface  of  the  inferior  maxillary 
division  of  the  fifth  nerve,  just  after  it  has  emerged  from 
sthe  cranium  throup^h  foramen  lacerum  basis  cranii. 


166-  OUTLINES   OF   EQUINE   ANATOMY. 


PAET   y.— SPECIAL   ANATOMY. 
The  Neck. 

From  tlie  incisiou  along  tlie  central  line  of  tlie  front  of 
tlie  neck  tlie  operator  dissects  tbe  skin  from  ^panniculus 
carnosus  in  an  upward  direction,  it  being  moderately  firmly 
attached  until  it  arrives  at  the  collection  of  cellulo- 
adipose  material  attached  to  the  superior  margin  of 
the  ligamentum  nuchse  along  the  greater  part  of  its. 
length,  which  is  somewhat  intimately  blended  with  the 
skin. 

Extending  from  the  root  of  the  ear,  parallel  to  the  pos- 
terior margin  of  the  lower  jaw,  is  parotideo-auricularis, 
attached  suj^eriorly  to  the  conchial  cartilage,  and  running 
downwards  to  be  attached  to  the  surface  of  the  parotid 
salivary  gland.  It  is  covered  by  a  thin  layer  of  panniculus. 
Behind  the  ear,  along  ligamentum  nuchsa  for  about  five 
inches,  are  attached  the  retrahentes  aurum  muscles  drawing 
back  the  ear. 

Along  the  lower  part  of  the  neck  the  muscular  fibres  of 
panniculus  are  distinct ;  anteriorly  some  of  them  assume 
a  somewhat  peculiar  arrangement,  running  in  a  different 
direction  to  the  other  fibres,  in  a  distinct  band,  towards 
the  submaxillary  space,  meeting  with  the  corresponding 
fibres  from  the  opposite  side ;  posteriorly  the  muscle  be- 
comes much  increased  in  thickness,  and  sends  some  mus- 
cular fibres  to  cover  the  anterior  part  of  the  connection  of 
pectoralis  transversus  with  the  cariniform  cartilage ;  its 
main  portion,  however,  extends  over  the  shoulder  with 
levator  humeri,  with  the  tendinous  j)art  of  which  muscle  it 
blends,  at  the  superior  j)art  of  the  neck,  and  so  the  pan- 
niculus carnosus  becomes  indirectly  attached  to  the  supe- 
rior margin  of  ligamentum  nuchse.  The  splenius  muscle 
may  be  seen  after  removal  of  the  skin  through  the  superior 
aj)oneurosis  of  the  levator  humeri. 


THE   NECK.  167 

On  removal  of  panniculus  we  disclose,  at  tlie  postero- 
superior  part,  the  sterno-maxillaris  shortly  after  its  origin 
from  the  anterior  extremity  of  the  cariniform  cartilage, 
blended  with  its  fellow  along  the  middle  line,  thus  forming 
a  sling  underneath  the  trachea,  about  the  anterior  part  of 
the  posterior  third  of  the  neck,  they  separate,  and,  becom- 
ing round  muscular  cords,  run  forwards  to  be  inserted  each 
by.a  broad  tendon,  which,  after  separating  the  parotid  from 
the  submaxillary  salivary  glands,  i^asses  over  stylo-maxil- 
laris,  and  becomes  attached  to  posterior  margin  of  the  lower 
jaw  about  three  inches  below  its  articulation  with  the 
squamous  temporal  bone. 

The  ti-achea  at  the  middle  third  of  the  neck  is  covered 
by  the  sterno-thyro-hyoideus  muscle,  which,  passing  from 
the  anterior  extremity  of    the   cariniform  cartilage,  here 
divides  into  two  parts  ;  the  thimier  runs  underneath  sub- 
scapulo-hyoideus  to  the  lateral  part  of  the  external  surface 
of  the  ala  of  the  thyroid  cartilage,  where  it  terminates, 
being  inserted  between  the  muscles  proper  to  the  larynx  : 
just  above  this  termination  is  situated  the  thyroid  body,  a 
small  dark-red  body  of  a  rounded  form  attached  to  the 
lateral  aspect  of  the  anterior  part  of  the  trachea.     The 
thyroid  body  under  the  microscope  presents  a  number  of 
vesicular  cavities  lined  by  tesselated  epithelium  embedded 
in  a  somewhat  soft  stroma.     It  is  one  of  the  so-called  vas- 
cular glands,  the  use  of  which  is  not  distinctly  understood, 
and  receives  a  large  hranch  from  the  carotid  arteri/,  the  only 
constant  one  given  off  from  that  vessel  in  its  course  up 
the  neck ;  this  branch  frequently  sends  off  a  twig  to  the 
larynx  which  receives  the  name  of  the  laryngeal  artery. 
The  broader   division  of    sterno-thyro-hyoideus    runs  to- 
wards  the  centre   of    the   submaxillary   space,   where    it 
becomes  inserted  into  the  under  surface  of  the  body  of  os 
sphenoides,  together  with    subscapulo  -  hyoideus,   which, 
however,  occupies  a  much  larger  surface  of  attachment, 
and  which  puts  in  its  appearance  about  the  anterior  third 
of  the  neck,  running  from   rmderneath  sterno-maxillaris 
to   meet    its   fellow   at   its  attachment.      By  removal  of 
parotideo-auricularis  and  panniculus,  the  parotid  gland  is 
exposed.     It  is  an  irregular- shaped  organ  of  a  dirty  white 
colour,  composed  of  numerous  minute  lobules,  which  fit  in 
between  the  different  structures  it  covers.     Anteriorly  it 
extends  a  little  on  to  the  surface  of  masseter  externus, 


168  OUTLINES    OF   EQUINE    ANATOMY. 

being  superiorly  m  contact  with  the  temporal  artery  and 
vem  and  facial  nerve  as  they  arise  and  wind  round  the 
jaw,  and  then  extends  upwards  over  the  muscles  in  front 
of  the  ear  forming  one  of  its  superior  divisions,  the 
other  being  situated  behind  the  ear.  From  this  the  j^os- 
terior  margin  of  the  gland  runs  in  a  downward  direction, 
being  separated  from  the  wing  of  the  atlas  by  tendinous 
structure,  and  terminates  at  the  junction  of  the  submaxil- 
lary and  jugular  veins,  from  which  point  its  lower  margin 
runs  forwards  to  the  angle  of  the  jaw.  From  this  antero- 
inferior point  the  duct  of  the  gland  arises,  and  passes  over 
the  internal  surface  of  the  lower  edge  of  masseter  internus, 
where  it  is  covered  only  by  panniculus  and  skin,  and  is 
in  company  with  the  submaxillary  artery,  and  the  corre- 
sponding vein.  Through  the  substance  of  the  parotid  run 
several  large  veins,  among  others  the  jugular,  and  by 
raising  it  and  removing  the  stylo-maxillaris,  running  from 
the  anterior  part  of  the  styloid  process  of  the  occiput  to 
the  angle  of  the  lower  jaw,  blending  superiorily  with  digas- 
tricus,  we  expose  the  termination  of  the 

Carotid  artery.  Just  oj^posite  to  the  commencement  of 
the  trachea  it  breaks  up  into  three  parts,  one. 

Ramus  anastomoticus,  runs  directly  upwards  to  the 
under  surface  of  the  wing  of  the  atlas  (giving  off  a  large 
branch  running  to  the  occiput),  here  it  rests  upon  obliquus 
capitis  anticus,  and  anatomoses  with  a  vessel,  the  vertebral 
artery,  coming  through  the  posterior  foramen  in  the  wing 
,of  the  atlas  ;  the  trunk  so  formed  passes  into  the  anterior 
foramen,  which  has  two  outlets,  through  one  of  which  a 
branch  runs  to  obliquus  capitis  inferior  upon  the  upper 
surface  of  the  atlas,  through  the  other  a  branch  passes 
.into  the  spinal  canal,  and  after  piercing  the  dura  mater 
;of  the  spinal  cord  anastomoses  with  its  fellow  from  the 
opposite  side  and  runs  forwards,  as  the  basilar  artery,  to 
supply  the  brain.  The  smallest  of  the  three  terminal 
branches  of  the  carotid,  the  internal  carotid,  runs  directly 
.towards  the  base  of  the  cranium  throughout  its  course 
being  situated  with  its  fellow  at  the  posterior  part  of  the 
septum  formed  by  the  contact  of  the  internal  walls  of  the 
two  guttural  pouches. 

The  external  carotid  seems  to  be  the  direct  continuation 
/Of  the  carotid  trunk,  it  passes  forwards,  and  just  before 
arriving  at  the  posterior  angle  of   the  long  cornu  of  os 


THE    NECK.  169 

liyoides  gives  off  tlie  submaxillary  artery,  wliicL,  running 
between  the  long  cornu  and  hyoideus  inagnus,.gives  off  the 
.lingual  artery  running  forwards,  and  then  meets  with  and 
accompanies  the  corresponding  vein,  and  the  parotid  duct 
over  the  internal  surface  of  the  inferior  margin  of  mas- 
seter  internus.  After  reaching  the  external  part  of  the 
dilated  superior  extremity  of  the  long  cornu,  the  external 
carotid  gives  off  large  posterior  masseter  Iranches  anteriorly, 
parotid  branches  and  branches  to  stylo-maxillaris  exter- 
nally, and  the  posterior  auricular  posteriorly.  This 
latter  branch  gives  off  the  middle  auricular,  which  runs 
to  the  external  auditory  opening.  The  external  carotid  is 
here  covered  by  the  mucous  membrane  of  the  guttural 
pouch,  a  transparent  layer  which  covers  both  sides  of  the 
long  cornu  of  os  hyoides ;  on  reaching  the  temporo- 
maxillary  joint  the  artery  terminates  in  three  branches,  the 
anterior  auricular,  which  runs  to  the  front  of  the  ear  to 
supply  the  structures  in  that  neighbourhood  ;  the  tem- 
poral, which  winds  round  the  jaw  and  runs  along  the 
superior  margin  of  masseter  externus  ;  and  the  internal 
maxillary,  which  runs  to  the  base  of  the  cranium. 

The  levator  humeri  must  now  be  dissected  to  its  attach- 
ment to  the  crest  of  the  occiput ;  to  the  mastoid  ridge  ex- 
tending downwards  laterally  from  that  ridge,  the  wing  of 
the  atlas  by  a  tendon  common  to  it  and  trachelo-mas- 
toideus  and  splenius,  the  transverse  processes  of  the  second, 
third,  and  sometimes  fourth  cervical  vertebrae.  By  turning 
up  its  inferior  margin  we  show  the  branches  of  the  cervical 
intervertebral  nerves  running  directly  to  it.  Its  attachment 
to  the  superior  margin  of  the  ligamentum  nuchse  by  f  aschia, 
and  its  blending  posteriorly  with  trapezius  may  also  be 
noticed  ;  by  this  time  its  attachments  to  the  fore  limb  will 
be  shown,  i.  e.  to  the  spine  of  the  scapula,  the  point  of  the 
shoulder,  the  humeral  ridge  with  its  elongating  ligament, 
and  the  antero-uiferior  depression  of  the  humerus. 

By  removal  of  levator  humeri  we  expose  a  second  layer 
-of  superior  cervical  muscles.  Eunning  from  the  transverse 
processes  of  the  cervical  vertebrae,  as  far  forwards  as  the 
third  to  the  superior  margin  of  the  scapula  is  serratus 
magnus,  and  from  the  antero- superior  angle  of  the  scapula 
rhomboideus  runs  in  the  form  of  an  extremely  elongated 
triangle  to  within  six  inches  of  the  attachment  of  the 
•cordiform  portion  of  the  ligamentum  nuchae  to  the  occiput. 


170  OUTLINES    OF   EQUINE   ANATOMY. 

Seen  between  tliese  muscles  and  covered  at  its  posterior 
part  by  them  is 

Splenins,  a  large  layer  of  muscle  attached  anteriorly,  in 
common  with  tracbelo-mastoideus,  to  tbe  mastoid  ridge,  tbe 
crest  of  tbe  occiput  and  the-  wing  of  tbe  atlas,  it  also  has 
heads  attached  to  the  transverse  processes  of  the  second, 
third,  fourth  and  fifth  cervical  vertebrae.  Posteriorly  it  is 
attached  to  the  superior  spinous  processes  of  the  three 
anterior  dorsal  vertebrae,  and  superiorly  to  the  cordifomi 
portion  of  ligamentum  nuchse  along  its  whole  length.  It 
posteriorly  sends  a  tendon  to  blend  with  the  commence- 
ment portion  of  the  dorsal  faschia.  Having  removed 
this  muscle  we  expose  another  muscular  layer  consisting 
mainly  of  complexus  major,  covered  inferiorly  against  the 
vertebrae  by 

Trachelo-mastoideus,  which  is  composed  of  three  distinct 
portions  :  1st.  Head  is  attached  with  splenius  to  the  mas- 
toid 2)i'ocess,  and  with  complexus  major  to  the  oblique 
processes  of  the  fourth,  fifth,  sixth  and  seventh  cervical 
vertebrae,  and  the  transverse  processes  of  the  two  anterior 
dorsal  vertebrae  :  2nd.  Head  with  splenius  to  the  trans- 
verse processes  of  the  two  anterior  and  separately  the 
oblique  processes  of  the  second,  third,  fourth,  fifth,  sixth 
and  seventh  ceiwical  vertebrae  ;  3rd.  Head  with  splenius  to 
fourth  ceiwical  transverse  process ;  the  second  and  third 
heads  join  with  the  first  to  become  attached  posteriorly. 
Between  the  superior  tendons  the  oblique  muscles  of  the 
head  are  to  be  seen. 

Obliquus  capitis  superior  arises  from  the  mastoid  ridge 
and  from  the  styloid  process  of  the  occiput,  its  fibres  run 
obliquely  downwards  and  backwards,  being  attached  inter- 
nally to  the  altoido-occipital  capsular  ligament,  and  be- 
come inserted  into  the  anterior  margin  of  the  transverse 
process  of  the  atlas,  at  the  inferior  margin  of  this  muscle, 
slightly  concealed  by  it,  is  a  small  muscular  band, 

Obliquus  capitis  anticus,  which  runs  from  the  styloid 
process  of  the  occiput  to  the  under  surface  of  the  body  of 
the  atlas  at  its  lateral  part — it  is  also  attached  to  the  cap- 
sular ligament  of  the  joint. 

Obliquus  capitis  inferior  passes  from  the  supero-ex- 
ternal  part  of  the  wdng  of  the  atlas,  over  the  altoido- 
dentatal  joint  to  the  capsule  of  which  it  is  attached,  and 
becomes  inserted  into    the  lateral  part  of    the    superior 


THE    NECK.  171 

spinous  process  of  the  dentata  ;  posteriorly  it  is  in  contact 
with  the  anterior  semi- spinalis  muscle  of  the  neck,  and  on 
the  wing  of  the  atlas  it  covers  the  vertebral  artery,  where  it 
passes  on  to  the  ala,  and  then  dips  down  through  its  pos- 
terior foramen  to  anastomose  with  ramus  anastomoticus. 
Through  the  anterior  foramen  a  branch  of  the  artery  runs 
from  the  union  of  these  two  to  the  muscles  situated  about 
here, .  but  the  main  portion  passes  through  the  foramen  in 
the  pedicle  of  the  atlas,  and  after  gaining  the  vertebral 
canal,  pierces  the  dura  mater,  and  uniting  with  its  fellow 
forms  the  basilar  artery,  which  runs  to  the  brain. 

Complexus  major  is  attached  in  common  with  trachelo- 
mastoideus  to  the  oblicjue  processes  of  the  fourth,  fifth, 
sixth  and  seventh  cervical  vertebrse,  and  the  transverse 
processes  of  the  two  anterior  dorsal  vertebrae.  It  is  also 
attached  to  the  oblique  processes  of  the  third,  fourth,  fifth 
and  sixth  dorsal  vertebrae,  and  to  the  oblic^ue  process  of  the 
third  cervical  vertebr£e  ;  anteriorly  it  blends  with  complexus 
minor,  and  becomes  inserted  into  the  scabrous  pit  of  the 
occiput.  It  is  attached  along  the  greater  part  of  the  supe- 
rior margin  of  ligamentum  nuchse.  Its  posterior  attach- 
ment is  covered  by  a  muscle  which  seems  at  first  sight  to 
be  a  part  of  longissimus  dorsi,  i.e.  cervico- dor  sails,  which 
is  attached  in  common  with  complexus  major  to  the 
oblique  processes  of  the  six  anterior  dorsal  vertebrae,  and 
runs  forwards  to  the  transverse  xH'ocesses  of  the  three  pos- 
terior cervical  vertebrae  (to  the  seventh  it  is  attached  by  a 
tendon,  which  it  shares  with  longissimus  dorsi). 

Complexus  minor  arises  from  the  posterior  part  of  the 
superior  spinous  processes  of  the  dentata,  and,  blending 
anteriorly  with  the  complexus  major,  becomes  inserted  into 
the  scabrous  pit  of  the  occiput.  It  lies  in  contact  with  its 
fellow  of  the  opposite  side,  for  about  here  the  ligamentum 
nuchse  is  deficient,  there  being  a  space  between  its  cordif orm 
and  membraniform  portions.     By  removal  of  it  we  expose 

Rectus  capitis  posticus  major,  running  from  the  ante- 
rior part  of  the  superior  spinous  process  of  the  dentata, 
becoming  attached  to  the  atloido-axoidal  capsular  ligament, 
and  blending  in,  become  inserted  into  the  scabrous  pit  of 
the  occiput  with 

Rectus  capitis  posticus  minor,  which  arises  from  the 
superior  part  of  the  arch  of  the  atlas,  and  is  attached  to  the 
atloido- occipital  capsular  ligament. 


17^  OUTLINES    OF    EQUINE    ANATOMY. 

The  jugular  vein,  after  2:>assing  tlirougli  the  parotid 
gland,  receives  the  submaxillary  vein  when  about  opposite 
-the  thyroid  body.  It  then  proceeds  down  the  channel  of 
the  neck,  receiving  no  important  branches,  until  it  arrives 
at  the  lower  part,  when  the  superficial  hrachial  vein,  which 
carries  blood  from  the  fore  extremity  opens  into  it,  and  in 
some  cases  it  receives  the  lymph  from  the  thoracic  duct  on 
the  left  side,  the  great  right  lymphatic  on  the  right  (often, 
however,  this  opens  into  the  axillary  vein) .  Finally,  be- 
tween the  two  first  ribs  the  jugulars  unite  to  form  the  com- 
mencement portion  of  the  anterior  vena  cava.  By  removing 
the  jugular  vein  aud  subscapulo-hyoideus  we  expose  the 
trachea,  and  on  its  supero -lateral  part  the  carotid  artery 
with  the  pneumogastric  and  gangliated  cord  of  the  sympa- 
-thetic  nerves  enclosed  in  its  sheath,  and  the  inferiof 
laryngeal  branch  of  the  pneumogastric  a  little  lower  down. 

The  (Esophagus  is  a  long  tube  which  commences  an- 
teriorly at  the  posterior  part  of  the  pharynx,  and  after 
passing  along  the  neck,  and  through  the  thorax,  and  the 
foramen  sinistrum  of  the  diaphragm,  terminates  at  the 
cardiac  or  left  opening  of  the  stomach.  At  first  situated 
above  the  larynx  in  its  course  down  the  neck,  it  becomes 
inclined  to  the  left  side  (thus  we  watch  the  left  side  of  the 
neck  to  see  a  ball  "  go  ")  so  that  on  entering  the  thorax  it 
is  near  the  inner  surface  of  the  first  left  rib.  While  pass- 
ing through  the  anterior  mediastinum  it  becomes  slightly 
above  the  trachea  inclined  to  the  right  side,  and  in  pass- 
ing over  the  base  of  the  heart  it  crosses  the  right  bronchus, 
-then  in  the  posterior  mediastium,  having  rested  in  a  special 
groove  in  the  left  lung,  where  it  is  in  company  with  the 
•pneumogastrics,  it  passes  with  them  through  foramen 
sinistrum.  It  consists  of  two  coats.  The  external  is  mus- 
cular, anteriorly  it  is  directly  continuous  Avith  crico-pharyn- 
geus ;  it  consists  of  longitudinal  fibres  externally  placed, 
circular  fibres  internally,  and  until  it  has  passed  over  the 
base  of  the  heart  it  retains  its  red  colour,  which  is  apt  to 
cause  it  to  be  mistaken  for  some  of  the  cervical  muscles  in 
the  neck.  Posteriorly  it  becomes  thicker,  and  its  fibres  are 
-continuous  with  those  of  the  stomach.  This  coat  is  con- 
nected to  the  internal  or  mucous  coat  by  very  loose  areolar 
'tissue,  in  consequence  of  which  the  latter  is  generally 
arranged  in  longitudinal  folds  which  close  the  cavity  of 
the  tube.     It  is  the  termination  of  this  mucous  coat  at  the 


THE    NECK.  173^ 

stomach  whicli  is  said  to  prevent  vomition  in  the  horse  except 
under  extreme  circumstances  ;  others  attribute  it  to  the 
mode  of  entrance  of  the  oesoj^hagus  into  the  stomach, 
while  some  argue  the  presence  of  a  special  spiral  valve. 
This  mucous  membrane  is  similar  in  structure  to  that  of  the 
pharynx  and  to  the  cuticular  portion  of  the  mucous  lining 
of  the  stomach,  with  which  it  is  continuous  anteriorly  and 
posteriorly  respectively. 

In  the  upper  and  anterior  part  of  the  neck,  perceptible 
on  manipulation  in  the  living  animal,  is  the  larynx,  a 
remarkable  cartilaginous  organ  the  seat  of  the  voice  ;  the 
upper  part  of  the  trachea  specially  modified.  It  is  com- 
posed of  several  pieces  of  cartilage,  which  are  united 
together  in  some  places  by  synovial,  in  others  by  fibrous 
articulations.  Elastic  expanded  ligaments  in  some  situa- 
tions strengthen  the  connection.  The  larger  cartilages  are 
five  in  number ;  thyroid,  cricoid,  two  arytenoids,  and  epi- 
glottis. The  Thyroid  is  the  largest,  and  consists  of  a  body 
and  two  wings.  The  body  is  supero -anteriorly  placed,  and 
is  the  thickest  portion  of  the  cartilage.  It  has  two  surfaces, 
anterior  and  posterior,  and  four  margins,  superior,  inferior, 
and  two  lateral.  To  the  internal  surface  the  epiglottis  is 
attached  by  elastic  tissue,  the  external  surface  is  in  contact 
with  the  sterno-thyro-hyoidei  muscles.  To  the  superior  mar- 
gin is  attached  the  thyro-hyoid  ligament,  to  the  inferior  mar- 
gin the  crico -thyroid  ligament,  and  the  aloi  or  ivings  arise  from, 
the  two  lateral  margins.  The  aloi  are  firm  flat  portions  of  the 
cartilage  which  exhibit  a  tendency  to  undergo  ossification  ; 
each  of  them  manifests  the  form  of  an  oblique-angled  paraL 
lellogram,  the  anterior  acute  angle  of  which  blends  with  the 
body  of  the  cartilage ;  the  postero-inferior  acute  angle  is 
rather  elongated,  and  presents  a  synovial  surface  for  articu- 
lation with  the  antero-inferior  synovial  facet  of  the  cricoid 
cartilage.  The  postero-superior  oblique  angle  presents  a 
flexible  cartilaginous  prolongation,  superior  cornu  of  the 
posterior  margin,  the  free  extremity  of  which  is  united  by 
fibro-cartilaginous  tissue  to  the  posterior  extremity  of  the 
heel  process  of  os  hyoides.  The  antero-inferior  oblique  angle 
forms  the  point  of  junction  of  the  anterior  and  inferior 
margins,  to  both  of  which  is  attached  the  crico-thyroid 
ligament.  The  superior  margins  of  the  two  alse  are  con- 
nected together  by  the  superior  extremity  of  the  body  and 
from  the  whole  ridge  thus  formed  the  thyro-hyoid  ligament 


174  OUTLINES    OF   EqUlXE    AK ATOMY. 

runs  to  the  posterior  crescentic  margin  of  the  hjoid  bone. 
This  ligament  fills  the  space  between  the  superior  cornu  of 
the  cartilage  and  the  alse,  with  the  exception  of  the  angle, 
where  it  is  deficient,  and  thns  a  foramen  is  formed  through 
wJiich  the  terminal  ])ortion  of  the  siijperior  laryngeal  branch  of 
the  imeumogastric  runs  to  supply  the  mucous  membrane  of 
the  larynx  with  exquisite  sensibility.  The  external  surface  of 
the  thyroid  alse  is  in  contact  with  the  thyro-hyoideus  supe- 
riorly ;  thyro-pharyngeus  supero-posteriorly  ;  crico-thyroi- 
deus  inferiorly  ;  between  these  the  short  portion  of  sterno- 
thyro-hyoideus  is  attached.  From  the  superior  cornu  the 
posterior  part  of  hyo-thyro-pharyngeus  runs  upwards.  The 
internal  surface  is  superiorly  covered  by  mucous  membrane, 
inferiorly  by  thyro-arytenoidei  posticus  and  anticus  (and  is 
in  contact  with  crico-ary  tenoideus  lateralis) .  The  Epiglottis 
has  aptly  been  likened  to  a  sage  leaf,  the  base  of  which 
is  attached  by  elastic  tissue  to  the  internal  surface  of  the 
body  of  the  thyroid,  the  apex  is  invested  closely  by  mucous 
membrane,  and  is  free.  It  consists  of  yellow  elastic  car- 
tilage, and  the  mucous  membrane  covering  it  presents 
very  large  mucous  gh.nds.  To  the  anterior  surface  mucous 
membrane  proceeds  from  the  base  of  the  tongue,  and  by 
removal  of  this  centrally  we  shall  expose 

Syo-eijiglottideus  running  from  the  posterior  part  of  the 
body  of  OS  hyoides,  directly  backwards  to  the  anterior  sur- 
face of  the  epiglottis.  The  base  of  the  epiglottis  on  either 
side  is  continued  by  a  prolongation  which  runs  in  a  back- 
ward direction,  connected  by  cartilaginous  nodules  (called 
the  cuneiform  cartilages)  to  the  arytenoid  cartilages.  The 
posterior  surface  of  the  epiglottis  is  covered  by  mucous 
membrane,  and  during  the  act  of  deglutition  is  brought 
down  over  the  glottal  opening  or  entrance  to  the  larynx. 

The  cricoid  cartilage,  as  its  name  indicates,  is  extremely 
like  a  finger-ring.  Its  smallest  part  is  anteriorly  situated, 
and  from  this  it  increases  in  size  irregularly  in  a  posterior 
direction.  The  posterior  part  forms  a  flat  hexagonal  sur- 
face, with  a  central  ridge  and  four  synovial  articulatory 
facets,  two  at  the  antero-inferior  angles  for  articulation 
mth  the  posterior  acute  angles  of  the  thyroid  alse,  two  at 
the  postero-superior  angles  for  articulation  with  the  ary- 
tenoid cartilages.  On  either  side  of  the  central  ridge  is 
attached  a  crico-arytenoideus  posticus,  while  crico-aryte- 
Tioideus  lateralis  originates  from  the  posterior  j^art  of  the 


THE    NECK.  175 

superior  margin  of  tlie  smaller  portion  of  the  cartilage. 
The  whole  interior  margin  affords  attachment  to  the  crico- 
trachealis  ligament,  the  anterior  part  of  the  superior 
margin  to  the  crico-thyroid  ligament.  The  lateral  parts  of 
the  external  surface  to  the  crico-thyroid  muscles.  The 
internal  surface  is  lined  by  mucous  membrane. 

The  arytenoid  cartilages,  two  in  number,  articulate 
inferiorly  by  synovial  joints  with  the  cricoid  cartilage.  The 
articulatory  part  is  shaped  like  a  prism,  the  inner  angle  of 
which  is  elongated  in  a  posterior  direction  towards  its 
fellow;  the  outer  angle  in  an  anterior  direction  towards 
the  epiglottis,  with  which  it  is  indirectly  connected  by  the 
above-mentioned  cartilaginous  nodules.  The  superior  ex- 
tremity of  the  prismatic  portion  is  expanded,  and  sends  a 
peculiar  thin  process  in  an  anterior  direction  to  be  united 
by  mucous  membrane  to  the  epiglottis.  Thus  the  external 
surface  presents  two  triangular  spaces,  into  the  posterior  of 
which  arytenoideus  is  attached  (running  from  one  cartilage 
to  the  other),  into  the  anterior  the  thyro-arytenoidei  j^os- 
ticus  and  anticus,  while  crico-arytenoidei  lateralis  and  pos- 
ticus are  attached  to  the  prominent  ridge  between  the  two. 
The  superior  margins  of  the  arytenoid  cartilages  are  con- 
nected by  continuity  of  their  investing  mucous  membrane. 

From  the  internal  surface  of  the  arytenoid  cartilages  to 
the  inner  surface  of  the  thyroid  cartilage  and  of  the  crico- 
thyroid ligament  run  bands  of  yellow  elastic  tissue  termed 
the  vocal  cords,  by  the  tension  of  which  the  sound  of  the 
voice  is  modulated.  They  are  covered  on  their  internal 
surface  by  the  laryngeal  mucous  membrane,  and  externally 
are  in  contact  with  the  thyro-arytenoidei  muscles  ;  the  tri- 
angular space  between  them  is  the  rima  glottidis.  In  our 
description  of  the  cartilages  we  have  incidentally  noticed 
the  different  layers  of  yellow  elastic  tissue  which,  while 
they  serve  to  connect  the  different  portions  of  cartilage 
together,  also  by  their  elasticity  cause  them  to  return  to 
their  normal  position  after  allowing  them  to  accommodate 
themselves  to  the  movements  of  the  neighbouring  parts. 
The  crico-thyroid,  crico-trachealis,  crico- arytenoid,  and 
thyro-hyoid  ligaments  therefore  require  no  further  descrip- 
tion. The  mucous  membrane  of  the  postero-inferior  part 
of  the  pharynx,  after  being  reflected  over  the  margin  of  the 
arytenoid  and  epiglottic  cartilages  before  investing  the 
vocal  cords    on  either  side,  presents  a  diverticulum,  the 


176  OUTLINES    OF    EQUINE    ANATOMY. 

ventricles  of  the  larynx,  which  are  suj)posed  to  give 
resonance  to  the  voice  ;  they  j^ass  down  between  the  thyro- 
arytenoidei  anticus  and  posticus,  and  in  the  upper  part  of 
each  in  the  ass  we  see  a  small  opening  leading  into  a 
secondary  cavity.  After  passing  over  the  cordse  vocales 
the  mucous  membrane  lines  the  inner  surface  of  the  cricoid 
cartilage,  and  is  continued  downwards  into  the  trachea. 

Thyro-hyoideus  arises  from  the  external  surface  of  the 
wing  of  the  thyroid,  and  runs  to  be  attached  to  the  heel 
process  of  os  hyoides ;  its  internal  surface  is  in  contact 
with  the  thyro-hyoid  ligament. 

Crico-thyroideus  runs  from  the  external  surface  of  the 
lateral  part  of  the  cricoid  to  the  posterior  part  of  the  inferior 
border  of  the  wing  of  the  thyroid. 

Crico-arytenoidens  posticus  arises  from  the  superior 
surface  of  the  posterior  hexagonal  part  of  the  cricoid,  and 
its  fibres  converge  to  become  inserted  into  the  central 
ridge  on  the  external  surface  of  the  arytenoid,  in  common 
with 

Crico-arytenoideus  lateralis,  which  arises  from  the 
superior  margin  of  the  cricoid  at  the  lateral  part.  Ary- 
tenoidens  runs  from  the  external  surface  of  one  arytenoid 
to  that  of  the  other,  consisting  really  of  two  muscles 
blending  along  the  central  line. 

Thyro-arytenoidei  posticus  and  anticus  (generally  con- 
sidered as  one  muscle)  are  separated  by  the  inflection  of 
mucous  membrane,  which  forms  the  ventricle  of  the  larynx. 
They  arise  from  the  internal  surface  of  the  thyroid,  and 
run  to  the  anterior  part  of  the  external  surface  of  the 
arytenoid. 

The  trachea  is  a  large  tube  through  which  air  passes  in  its 
l^assage  from  the  larynx  into  the  lungs  and  vice  versa.  It  is 
composed  of  a  series  of  cartilaginous  rings,  fifty  to  sixty  in 
number,  which  are  embedded  in  and  connected  together  by  a 
quantity  of  yellow  elastic  tissue.  These  rings  are  thickest  in- 
feriorly,and  superiorly  are  deficient, being  terminated  by  two 
thin  expanded  extremities  which  overlap  each  other,  and  are 
connected  together  by  loose  areolar  tissue.  Anteriorly  the 
trachea  commences  by  being  connected  to  the  inferior  mar- 
gin of  the  cricoid  cartilage  by  the  crico-trachealis  ligament y 
which  allows  considerable  motion  between  the  two.  Pos- 
teriorly after  crossing  the  base  of  the  heart  in  the  thorax^ 
where  it  is  situated  between  the  large  arteries  at  their  com- 


THE    NECK.  177 

mencement  and  tlie  large  veins  at  their  termination,  it  ter- 
minates, forming  the  two  bronchi,  round  cartilago- elastic 
tubes  running  to  the  lungs.  Its  last  cartilaginous  ring  is 
different  from  the  rest,  since  it  forms  a  species  of  sac  from 
either  side  of  which  a  bronchus  passes,  the  right  opening 
being  the  largest.  The  trachea  therefore  passes  down 
the  neck  slightly  inclined  to  the  right  side  ;  superiorly  it 
is  in  contact  with  the  longi  colli  muscles,  laterally  with 
the  carotid  arteries,  the  pneumogastric,  recurrent,  and 
sympathetic  nerves,  and  on  the  left  side  with  the  oesophagus. 
The  jugular  veins  are  in  contact  with  its  lateral  part 
superiorly  and  inferiorly,  but  at  the  centre  are  separated 
by  the  subscapulo-hyoidei  muscles.  Sterno-maxillaris  and 
sterno-thyro-hyoideus  respectively,  by  blending  with  their 
fellows,  help  to  support  it.  In  passing  between  the  first 
ribs  it  is  superiorly  placed  to  the  commencement  portion 
of  the  anterior  vena  cava,  and  to  the  termination  of  the 
arteriae  innominatse,  and  here  the  oesophagus  passes  over 
it  to  gain  the  right  side.  At  its  extreme  upper  -psivt  the 
oesophagus  is  superiorly  placed,  and  the  thyroid  bodies  on 
either  side  generally  connected  by  a  central  portion  which 
runs  round  its  inferior  face.  On  the  inner  surface  of  the 
trachea,  running  from  one  side  to  the  other  at  its  superior 
3)art,  is  a  continuous  layer  of  transverse  unstriated  mus- 
cular fibres  termed  trachealis  transversus ;  the  outer  surface 
of  this  muscle  is  connected  to  the  cartilages  by  extremely 
loose  areolar  tissue,  while  its  inner  surface  is  covered  by  the 
mucous  membrane  which  lines  the  trachea,  and  which 
presents  ciliated  columnar  epithelium.  The  pneumo- 
gastric nerve,  after  emerging  from  the  cranium  through 
foramen  lacerum  basis  cranii,  and  sending  numerous  fibres 
to  the  neighbouring  nerves  and  ganglia,  gives  off  the 
superior  laryngeal  nerve ;  it  then  runs  down  the  neck  in  a 
sheath  with  the  carotid  artery  and  the  recurrent,  and  sym- 
pathetic nerves.  The  recurrent  is  the  inferior  laryngeal 
nerve,  and  supplies  all  the  intrinsic  muscles  of  the  larynx 
ivith  motor  poiuer  except  crico-thyroideus,  ivhich  receives  a 
branch  from  the  superior  laryngeal.  The  left  recurrent 
nerve  is  involved  in  the  disease  termed  "  roaring,"  whence 
jjaralysis  and  fatty  degeneration  of  the  muscles  supplied 
by  it  ensues  especially  of  the  crico-  and  thyro-arytenoidei 
muscles.  The  superior-laryngeal  nerve  is  compound  at 
its  origin ;  on  arriving  at  the  larynx  it  supplies  some  of 

1^ 


178  OUTLINES   OF   EQUINE   ANATOMY. 

the  pharyngeal  muscles,  and  thyro-hoideus  and  crico-thy- 
roideus,  and  then  becoming  purely  sensory  pierces  the  fora- 
men beween  the  thyroid  cornu  and  the  wing  of  the  thyroid,, 
and  supplies  the  lining  mucous  membrane.  The  carotid 
artery  in  passing  wp  the  neck  along  the  lateral  part  of  the 
trachea  gives  branches  to  the  oesophagus  and  other  neigh- 
bouring structures,  but  the  only  constant  branch  is  one 
which  runs  to  the  thyroid  body,  and  which  also  sends  off 
a  large  branch,  the  laryngeal,  to  the  larynx.  Along  the 
under  surface  of  the  vertebrae  runs  Longus  colli,  which 
anteriorly  extends  to  the  tubercle  or  inferior  spinous  pro- 
cess of  the  atlas,  and  runs  as  far  back  as  the  sixth  dorsal  ver- 
tebra, becoming  attached  to  the  under  surface  of  the 
bodies  and  transverse  processes,  and  inferior  spinous  pro- 
cesses (except  sixth  cervical)  of  all  the  intervening 
vertebrae.  It  lies  in  contact  with  its  fellow  internally,  and 
its  thoracic  portion  is  covered  by  pleura  and  forms  a  some- 
what remarkable  prominent  cylindrical  muscular  mass.  On 
its  external  surface  posteriorly  just  in  front  of  the  first 
rib  we  see  the  vertebral  artery  and  vein  in  their  course 
between  the  canal  through  the  sixth  cervical  transverse 
process  and  the  entrance  to  the  thorax.  With  them  runs 
a  nerve  formed  by  union  of  a  branch  from  each  cervical 
nerve,  through  the  middle,  to  the  inferior  cervical  ganglion 
— both  of  which  ganglia  are  situated  between  the  two  first 
ribs.     These  structures  are  hid  from  view  by 

Scalenius,  a  muscle  composed  of  two  distinct  heads,  the 
superior  or  shorter  arises  from  the  transverse  j^rocess  of 
the  seventh  cervical  vertebra  and  runs  to  the  anterior 
margin  of  the  inferior  extremity  of  the  su23erior  third 
of  the  first  rib ;  the  longer  or  inferior  arises  from  the 
transverse  processes  of  the  fourth,  fifth,  and  sixth 
cervical  vertebrae,  and  its  fibres  converge  to  become  in- 
serted into  the  superior  part  of  the  inferior  third  of  the 
external  surface  of  the  first  rib.  Between  the  two  heads  the 
axillary  ^plexus  of  nerves  ]jasses,  heloio  the  inferior  head,  the 
axillary  artery  and  vein,  the  latter  heincj  inferiorly  sitimted. 
On  removal  of  this  muscle  we  see  the  origin  of  the  axil- 
lary plexus  from  the  sixth,  seventh,  and  eighth  cervical, 
and  first  dorsal,  and  sympathetic  nerves,  and  the  phrenic, 
running  in  a  direction  backwards,  having  originated  by 
fibres  from  the  fourth,  fifth,  and  sixth  cervical.  At  the 
janterior  part  of  the  neck  longus  colli  is  covered  by  the 


THE    NECK.  179 

Rectus  capitis  anticus  major,  wliicli  arises  from  tlie 
transverse  processes  of  the  third,  fourth,  and  fifth  cervical 
vertebr£e,  and  becomes  inserted  into  the  under  part  of  the 
posterior  extremity  of  the  body  of  the  s23henoid  bone. 
Just  behind  this 

Rectus  capitis  anticus  minor  is  inserted  into  the  antero- 
inferior part  of  the  basilar  process  of  the  occiput,  running 
from  the  under  surface  of  the  body  of  the  atlas,  and 
becoming  attached  to  the  atloido-occipital  capsular  liga- 
ment in  its  course.  The  inferior  surface  of  these  muscles 
is  covered  by  the  mucous  membrane  of  the  guttural  pouch, 
and  is  in  contact  with  numerous  large  nerves,  the  internal 
carotid  artery,  and  the  superior  cervical  ganglion,  a  grey 
nodular  body,  from  which  the  gangliated  cord  of  the 
sympathetic  commences  its  cervical  portion. 

The  supero-posterior  part  of  the  neck  is  supplied  with 
blood  by  the  posterior  cervical  artery.  It  commences  from 
the  antero-suj)erior  part  of  the  arteria  innominata,  on  the 
left  side  separately,  on  the  right  side  by  a  root  common  also 
to  the  anterior  dorsal  artery.  It  passes  upwards  through  the 
first  intercostal  space,  giving  off  the  first  intercostal  artery. 
It  then  passes  forwards  and  upwards  over  cervico-dorsalis, 
and  subsequently  runs  between  ligamentum  nuchse  and 
complexus  major  to  anastomose  with  the  artery  of  the 
poll. 

The  infero-j^osterior  part  is  supplied  by  the  inferior 
cervical  artery,  which  shortly  after  its  origin  from  the 
arteria  innominata  passes  forwards,  and  breaks  up  in  sup- 
plying the  muscles  in  this  neighbourhood  —  panniculus 
carnosus,  pectorales  transversus  and  anticus,  sterno-maxil- 
laris,  &c.  Three  sets^of  intrinsic  muscles  of  the  neck  require 
to  be  noticed : 

Intertransversalis  colli  passes  from  the  transverse  pro- 
cess of  one  vertebra  to  that  of  the  vertebra  next  in  order 
to  it. 

Spinalis  colli  runs  from  the  oblique  process  of  one  bone 
to  the  transverse  process  of  the  vertebra  second  in  order 
behind  it. 

Semispinalis  colli  from  the  superior  spinous  process  of 
one  vertebra,  passing  over  two  bones,  gains  the  oblique 
process  of  the  third  in  order. 

We  have  now  arrived  at  the  cervical  portion  of  the  spinal 
column  ;  by  sawing  through  the  laminse  of  the  vertebrse  on 


180  OUTLINES    OF   EQUINE   ANATOMY. 

•eitlier  side  we  may  expose  tlie  spinal  cord,  in  situ,  covered 
"by  its  membranes.  The  dura  mater  of  the  cord  differs 
from  that  of  the  brain  in  that  it  does  not  form  the  peri- 
osteum lining  the  bony  cavity  in  which  it  is  placed.  It  is 
continuous  anteriorly  with  the  corresponding  membrane 
of  the  brain,  in  passing  to  the  margin  of  foramen  mag- 
num of  the  occiput.  Posteriorly  it  forms  the  fihim  ter- 
w^inale  in  becoming  attached  to  the  posterior  extremity 
of  the  bony  canal.  On  either  side  it  is  closely  attached  to 
the  intervertebral  foramina,  and  is  reflected  across  these 
openings  to  close  them,  so  that  here  it  is  thick,  and  pre- 
sents two  rows  of  foramina,  through  which  the  collections  of 
nei-ve-fibres  pass.  The  pia  mater  is  directly  continuous 
with  that  of  the  brain  and  closely  invests  the  cord.  It  in 
structure  closely  resembles  that  of  the  brain,  and  laterally 
is  connected  to  the  dura  mater  by  the  ligamentum  denti- 
«culatum.  This  is  a  band  of  white  fibrous  tissue  extending 
along  the  lateral  part  of  the  cord,  attached  to  the  external 
surface  of  the  pia  mater,  between  the  superior  and  inferior 
roots  of  the  nerves.  It  sends  processes  outwards  opposite 
the  bodies  of  the  vertebrae,  which  become  attached  to  the 
inner  surface  of  the  dura  mater.  The  arachnoid  mem- 
l)rane  is  continuous  with  the  cranial  arachnoid,  lines  the 
dura  mater,  covers  the  pia  mater  loosely  so  as  to  j)roduce 
.a  suharaclmoid  space,  and  invests  the  processes  of  liga- 
iQientum  denticulatum,  and  those  portions  of  the  nerves 
■which  pass  through  the  arachnoid  space. 

The  Spinal  cord  consists  of  a  number  of  nerve-centres 
united  together  by  white  fibrous  nerve  cords,  which  render 
it  a  continuous  and  extremely  elongated  mass  extending 
irom  the  brain  anteriorly,  through  the  spinal  column  as  far 
rfxs  ahout  opposite  the  second  sacral  hone.  It  varies  in  size  in 
'different  parts,  and  this  variation  is  due  to  the  number  of 
aierves  it  must  give  off.  Thus  those  parts  which  supply 
merves  to  the  fore  and  hind  extremities  are  very  large.  It 
is  moderate  in  size  in  the  central  part  of  the  cervical  region, 
Ibut  in  the  posterior  cervical  and  anterior  dorsal  vertebrae 
it  grows  larger,  and  from  this  decreases  in  size  until  the 
lumbar  region,  where  it  becomes  large  in  giving  off  nerves 
-to  the  hind  limb.  As  a  rule  the  nerves  pass  straight  out- 
wards to  the  intervertebral  foramina,  but  in  the  sacral  region 
Ihey  run  obliquely  backwards,  and  the  superior  fibres  unite 
with  the  inferior  and  again  separate,  forming  the  superior 


THE   NECK.  181 

branches  wHcli  pass  tlirough  tlie  supersacral,  tlie  inferior 
through  the  subsacral  foramina.     In  all  other  regions  this 
union  and  subsequent  separation  occurs  after  the  nerves 
have  pierced  the  dura  mater  in  passing  through  the  inter- 
vertebral foramina.     This  arrangement  of  the  nerve-fibres 
in  an  oblique  direction  in  the  sacral  region  forms  the  caudco 
equina.     The  spinal  cord  consists  of  two  hemispheres  j^laced 
side  by  side,  separated  superiorly  by  the  superior  longitu- 
dinal fissure,  inferiorly  by  the  inferior  longitudinal  fissure^ 
the  latter  is  shallower  and  broader  than  the  former.     They 
are  separated  by  a  transverse  band  connecting  the  hemi« 
spheres,  termed  the  commissure,  which  consists  of    grey 
matter  Avith  white  substance  on  each  surface,  of  which  only 
the  superior  layer  is  thick  enough  to  be  visible  to  the  naked 
eye.     A  transverse  section  of  the  cord  shows  that  centrally 
it  presents  grey  matter  arranged  like  inverted  commas  in 
the  hemispheres,  connected  by  the  grey  commissure  the 
convex  surface  of  one  to  that  of  the  other.     Thus  the  grey- 
matter  presents  two  cornua  in  each  hemisphere.    The  superior 
is  the  longest  and  narrowest,  and  runs  upwards  and  out- 
wards, reaching  the  surface  of  the  cord.     The  inferior  is 
rounded  and  separated  from  the  surface  by  a  layer  of  white 
matter.     From  the  superolateral  part  of  the  cord  to  which 
the    superior  cornu  approaches  the    superior  nerve -fibres 
arise  from  the  whole  length  of  the  cord,  while  from  the 
infero-lateral  part  nearest  the  inferior  cornu  the  inferior 
fibres  arise.     The  superior  or  sensory  fibres  are  divided  into 
sets  which  converge  towards  the  intervertebral  foramina. 
They  pass  through  the  superior  openings  in  the  dura  mater, 
have  a  ganglion  in  connection  with  them,  and  are  micro- 
scopically indistinguishable  from  the  inferior  or  motor  fibres-^ 
which  run  from  the  cord  through  the  inferior  row  of  open- 
ings in  the  dura  mater  to  subsequently  unite  with  the  supe- 
rior fibres  forming  the  spinal  nerves.     By  this  arrangernent 
of  the  nerve-fibres  each  hemisphere  of  the  cord  is  divided 
into   a   superior,  a  middle   and  an  inferior  column.     The 
spinal  nerves  at  the  commencement  send  fibres  or  receive 
fibres  from  the  nearest  sympathetic  ganglion.     In  most 
regions  the    ganglia  of   the    sympathetic  cord    are  close 
against  the  intervertebral  foramina,  but  in  the  neck  the 
fibres  from  each  nerve  unite  to  form  a  branch  running  witb 
the  vertebral  artery  through  the  foramina  in  the  transverse 
processes  of  the  vertebrae  to  terminate  at  the  inferior  cer* 


182  OUTLINES   OF   EQUIN'E   ANATOMY. 

Tical  ganglion.  The  cervical  nerves  are  eight  in  number. 
The  first  or  suboccipital  emerges  through  the  foramen  in 
the  pedicle  of  the  atlas,  through  which  the  vertebral  artery 
gains  the  spinal  canal.  It  sends  fibres  to  the  auricular 
nerves  and  to  the  superior  cervical  ganglion  (situated  under- 
neath the  ala  of  the  atlas) .  The  second  nerve  emerges  through 
the  foramen  in  the  anterior  part  of  the  pedicle  of  the  den- 
tata.  The  third,  fourth,  and  fifth  nerves  send  fibres  to  form 
the  phrenic  nerve,  while  fibres  from  the  sixth,  seventh,  and 
eighth,  first  dorsal,  and  sympathetic  form  the  axillary  plexus. 
Each  of  these  nerves  after  passing  through  its  foramen 
sends  oif  a  superior  branch  to  the  structures  above  the  ver- 
tebrae, an  inferior  to  those  below.  On  the  lateral  part  of 
the  cord  as  far  down  as  the  fifth  cervical  vertebra  may  be 
seen  the  spinal  accessory  nerve  which  j^asses  upwards,  be- 
tween the  superior  and  the  inferior  roots  of  the  nerves, 
receiving  fibres  along  its  whole  course  from  the  cord  as  far 
up  as  the  medulla  oblongata. 

After  removing  the  cord  and  its  membranes  we  may  ex- 
amine the  superior  vertebral  ligament,  which  extends  along 
the  upper  surfaces  of  the  vertebrae  throughout  the  whole 
canal.  It  becomes  widened  in  becoming  attached  to  each 
intervertebral  cartilage  and  is  attached  to  the  roughened 
line  on  the  centres  of  the  upper  part  of  the  bodies  of  the 
vertebrae,  having  on  either  side  a  venous  sinus  extending 
along  the  whole  length  of  the  canal,  sending  a  transverse 
communicating  branch  under  this  ligament  opposite  the 
centre  of  the  body  of  each  vertebra — also  sending  branches 
outwards  through  each  intervertebral  foramen.  These 
sinuses  anteriorly  through  the  medium  of  the  posterior 
petrosal  sinuses  are  connected  to  the  cavernous  sinus. 


THE   BACK.  183 


PART    yi.— SPECIAL  ANATOMY. 
The  Back. 

By  dissecting  the  skin  from  the  lateral  thoracic  incision 
to  the  middle  line  of  the  back  the  panniculus  is  first  ex- 
posed, and  then  the  manner  in  which,  by  uniting  with  the 
combined  ajDoneurotic  exjDansions  of  latissimus  dorsi,  the 
two  small  serrati  (or  superficialis  costarum),  and  the  dorsal 
trapezius,  it  forms  the  lumbar  faschia,  which  extends  along 
the  whole  length  of  the  back,  from  the  shoulders  to  the 
quarters,  where  it  blends  with  the  gluteal  investing  layer. 
It  is  attached  to  the  superior  spinous  ligament  and  extends 
about  six  inches  on  either  side  of  the  sj^ine. 

Having  divided  panniculus  and  thrown  it  back,  leaving 
it  attached  to  the  lumbar  faschia,  we  expose  latissimus 
dorsi,  running  from  about  the  centre  of  the  mass  of  muscle 
forming  the  shoulder.  Its  muscular  portion  terminates 
about  opposite  the  eighth  rib,  where  it  blends  with  the 
lumbar  faschia.  Superiorly  situated  to  this  is  trapezius,  a 
triangular  muscle,  the  apex  of  which  is  fixed  to  the  tubercle 
on  the  spine  of  the  scapula,  its  base  to  the  superspinous 
ligament  blending  with  the  lumbar  faschia  posteriorly,  an- 
teriorly covered  by  levator  humeri,  and  with  it  attached  to 
the  cordiform  upper  portion  of  ligamentum  nuchse.  Its 
tendinous  portion  extends  from  its  apex  to  its  base  at  the 
withers,  thus  dividing  the  muscular  portion  into  two 
parts. 

The  posterior  small  serratus  is  exposed  to  view  by  re- 
moval of  panniculus.  It  presents  a  serrated  margin  infe- 
riorly,  its  fibres  runnmg  in  an  upward  direction  from  the 
posterior  margins  of  the  seven  posterior  ribs  to  the  lumbar 
faschia. 

Below  this  we  see  the  external  intercostals  running  in  a 
downward  and  backward  direction  from  the  posterior 
.margin  of  one  rib  to  the  anterior  margin  of  the  next.  Still 


184  OUTLINES    OF   EQUINE   ANATOMY. 

lower,  attaclied  to  tlie  inferior  extremity  of  the  external 
surface  of  the  ribs,  is  the  serrated  margin  of  obliquus  ab- 
dominns  externus.  Having  cut  through  and  dissected 
back  latissimus  dorsi  and  trapezius,  the  operator  must 
show  the  posterior  attachment  of  rhomboideus  muscle, 
which  arises  from  the  cordiform  portion  of  the  ligamentum 
nuchse  to  within  six  inches  of  the  occiput,  and  from  the 
continuation  of  it  as  far  back  as  the  sixth  dorsal  superior 
spinous  process,  from  which  points  it  runs  to  become  in- 
serted into  the  venter  surface  of  the  cartilage  of  elongation 
of  the  scapula,  and  to  that  bone  above  serratus  magnus. 
Now  rhomboideus  may  be  cut  through,  and  the  fore  limb 
(if  not  by  this  time  separated)  may  be  drawn  downwards, 
and  serratus  magnus  traced  to  its  inferior  attachments. 
We  now  see  the  small  anterior  serratus  muscle  running 
from  the  anterior  border  of  the  ribs  from  the  sixth  to 
twelfth  become  attached  by  tendinous  expansion  superiorly 
to  the  superior  spinous  processes  of  the  dorsal  vertebrae 
from  the  second  to  the  thirteenth.  By  dividing  the  dorsal 
and  lumbar  faschia  and  turning  the  serrati  downwards 
upon  their  inferior  attachments  we  expose 

Transversalis  eostarum,  a  thin,  complex  muscle,  about 
two  inches  broad,  anteriorly  attached  to  the  transversa 
process  of  the  last  cervical  vertebra,  in  common  with  lon- 
gissimus  dorsi,  and  by  small  tendons  attached  to  small 
roughened  surfaces  on  the  posterior  margin  of  all  the  ribs- 
(in  the  first  at  the  tubercle).  By  muscular  attachments  it 
is  connected  to  the  anterior  margin  of  the  ribs  as  high  up 
as  their  tubercles.  Posteriorly  it  becomes  attached  to  the 
transverse  processes  of  the  anterior  lumbar  vertebrae.  Its 
internal  surface  rests  on  the  external  intercostals,  while  its 
superior  margin  is  in  direct  contact,  and  almost  blends 
with 

Longissimus  dorsi.  This  is,  posteriorly,,  an  immense 
fleshy  mass  situated  at  the  posterior  part  of  the  back  and 
on  the  upper  surface  of  the  lumbar  vertebrae ;  it  is  the 
largest  muscle  in  the  horse's  body,  and  is  attached  to  thet 
crista  of  the  ilium,  extending  from  the  antero-inferior 
to  the  supero-posterior  spinous  j^i'ocess,  and  occupying  a 
slight  portion  of  its  venter  surface,  whereby  it  become?? 
attached  to  the  sacro-iliac  ligament  and  the  transverse 
oblique  and  superior  spinous  process  of  the  first  and  second- 
sacral  bones,  and  extends  backwards  into  the  triangular 


THE   BACK.  1-8^ 

space  on  tlie  supero-Lateral  part  of  tlie  sacrum,  where  it  is 
attached  to  the  sacral  and  to  the  ilio-sacral  ligaments.  It 
is  attached  to  the  transverse,  oblique,  and  superior  spinous 
processes  of  all  the  lumbar  and  of  the  posterior  dorsal  ver- 
tebrae, to  the  posterior  part  of  the  heads  of  all  the  ribs,  and 
to  the  transverse  processes  of  the  twelve  anterior  dorsal 
vertebrse,  and  the  last  cervical  in  common  with  transversalis 
costarum.  At  its  anterior  part  it  is  separated  by  cervico- 
dorsalis  from  complexus  major ;  at  the  posterior  part  of  the 
withers  it  comes  in  contact  with 

Spinalis  dorsi,  which  receives  from  it  a  large  and  strong- 
tendon.  It  is  attached  posteriorly  to  the  summits  of  the 
twelve  anterior  superior  spinous  processes  of  the  dorsal 
vertebrge  and  to  the  posterior  margins  of  the  superior 
spinous  processes  of  the  six  anterior  of  these  bones. 
Anteriorly  with  ligamentum  nuchse,  it  becomes  attached  to 
the  superior  spinous  processes  of  the  three  posterior  cer-- 
vical  vertebrse.  This  muscle  internally  lies  in  contact  with 
its  fellow  of  the  opposite  side,  for  the  ligamentum  nuchse 
is  here  deficient. 

The  posterior  cervical  artery,  after  passing  between  the 
first  and  second  ribs,  and  giving  off  the  first  intercostal 
branch,  runs  over  spinalis  dorsi  to  reach  the  external  sur- 
face of  ligamentum  nuchse,  along  which  it  runs  up  the 
neck  parallel  to  the  vertebral  column.  It  arises  on  the 
right  side  by  a  root  common  to  it,  and  the  dorsal  artery, 
from  the  right  arteria  innominata,  round  the  common  root, 
the  recurrent  or  inferior  laryngeal  branch  of  the  right  pneu- 
mogastric  nerve  winds  from  without  inwards  and  then  runs 
up  the  neck;  on  the  left  side  these  two  arteries  arise 
separately,  for  the  left  recurrent  nerve  passes  round  the 
aorta.  The  dorsal  artery  gives  off  a  branch  which  runs- 
underneath  the  heads  of  the  ribs  to  meet  the  sixth  inter- 
costal artery,  the  first  given  off  by  the  posterior  aorta. 
From  this  arch  run  the  third,  fourth,  and  fifth  intercostals ; 
the  second  intercostal  is  the  next  branch  given  off  by  the 
dorsal,  which  subsequently  passes  over  cervico- dorsalis 
towards  the  withers.  By  removal  of  longissimus  dorsi  and 
transversalis  costarum  we  show  a  series  of  muscles  running- 
obliquely  downwards  and  backwards  from  the  superior 
spinous  processes  to  the  oblique  processes  of  the  vertebrse, 
and  on  examination  we  find  this  arrangement  obtains  in;'^ 
the  cervical  lumbar  and  dorsal  regions  constituting  the 


186  OUTLINES    OF    EQUINE    ANATOMY. 

Semispinales  colli,  dor  si,  et  lumborum,  wliicli  com- 
mences at  the  superior  spinous  process  of  the  dentata  and 
extends  to  the  sacrum.  It  is  composed  of  a  chain  of  muscu- 
lar fasciculi,  which  run  obliquely  downwards  and  bachwards 
from  the  superior  spinous  processes  of  the  vertebrae  to  the 
oblique  processes  of  the  vertebrae  posteriorly  placed  to  these, 
sometimes  passing  over  two  or  three  prior  to  insertion.  A 
somewhat  similar  muscle  is 

Intertransversales  colli,  dorsi,  et  lumborum,  which  is 
composed  of  a  series  of  fasciculi,  which  in  the  neck  are 
situated  between  the  transverse  processes  of  the  vertebrae, 
in  the  back  are  blended  with  levatores  costarum,  and  in  the 
loins  are  found  between  the  transverse  processes. 

Levatores  costarum  are  a  series  of  small  triangular 
muscles  arising  from  the  transverse  processes  of  the  dorsal 
vertebrae,  and  running  to  the  anterior  border  and  external 
surface  of  the  ribs  as  high  up  as  their  necks ;  superiorly 
they  blend  with  intertransversales  dorsi,  and  they  are 
merely  the  superior  parts  of  the 

Intercostales  externi,  which  consist  of  muscular  and  ten- 
dinous fibre  intermixed,  which  run  obliquely  downwards 
and  backwards  from  the  posterior  margin  of  one  rib  to  the 
anterior  margin  of  the  rib  immediately  posterior  to  it. 
They  extend  no  lower  than  the  inferior  extremities  of  the 
ribs,  for  between  the  cartilages  the 

Intercostales  interni  fill  the  intervening  spaces  with 
fibres  running  obhquely  downwards  and  forwards.  Those 
portions  of  these  muscles  situated  between  the  sterno- 
costal cartilages  (which  are  attached  inf eriorly  to  the  lateral 
parts  of  the  sternum)  are  termed  sterno-costales  externi. 
From  this  point  upwards  we  see  the  internal  intercostals 
situated  internally  to  the  external  intercostals,  the  artery, 
vein,  and  nen^e  being,  during  a  considerable  part  of  their 
course,  between  the  two  muscular  layers  thus  formed.  The 
pleura  costalis  covers  the  inner  surface  of  the  internal 
intercostals. 

The  source  of  the  intercostal  arteries  has  been  already  in- 
dicated. From  their  origin  they  run  over  the  lateral  part 
of  the  bodies  of  the  dorsal  vertebrae,  giving  off  medullary 
tranches  to  these  bones ;  of  those  intercostals  which  arise 
from  the  posterior  aorta  the  right  are  somewhat  the  longest, 
and  before  reaching  the  intercostal  spaces  pass  above  the 
thoracic  duct  and  vena  azygos.     In  passing  the  interver- 


THE   BACK. 


18T 


tebral  foramen,  the  artery  gives  off  a  branch  which  imsses 
inwards  to  siipijly  the  sjmial  cord  and  its  membranes.  It 
next  sends  a  large  branch  to  the  muscles  of  the  baclc,  and  on 
£rst  gaining  the  intercostal  space  is  at  the  anterior  margin 
of  the  rib  behind,  but  soon  gains  the  posterior  margin  of 
the  rib  in  front,  along  which  it  passes  protected  by  the  bony 
groove,  and  by  the  intercostal  muscles,  between  which  it  is 
placed.  It  sends  ramuscules  to  the  ])leura,  muscles,  ribs, 
and  skin  in  the  neighbourhood,  and  the  anterior  intercostals 
help  to  supxDly  serratus  magnus ;  they  are  therefore  the 
largest.  At  the  inferior  part  of  the  intercostal  spaces 
these  vessels  anastomose  with  the  internal  thoracic  artery 
anteriorly,  posteriorly  with  that  branch  which  it  sends 
along  the  inferior  extremities  of  the  false  ribs.  Thus  the 
posterior  intercostals  indirectly  supply  the  abdominal  mus- 
cles and  anastomose  with  the  lumbars,  circumflex  ^  of  the 
ilium,  epigastric,  and  abdominal  branch  of  the  internal 
thoracic. 

The  intercostal  veins,  after  accompanying  the  arteries 
as  far  as  the  thorax,  for  the  most  part  empty  themselves 
into  the 

Vena  azygos,  a  vessel  which  arises  under  the  loins  and 
passes  with  the  thoracic  duct  and  posterior  aorta  through 
the  hiatus  aorticus  (a  foramen  of  the  diaphragm)  into  the 
thorax,  where  they  pass  in  the  superior  part  of  the  medias- 
tinum underneath  the  bodies  of  the  dorsal  vertebrae,  vena 
azygos  being  on  the  right,  posterior  aorta  on  the  left,  and 
the  thoracic  duct  centrally  placed.    This  vein  passes  to  the 
anterior  vena  cava,  with  one  of  the  branches  of  which  it 
communicates  by  means  of  a  subcostal  branch,  into  which 
the  third,  fourth,  and   fifth   intercostal  veins  pass,  thus 
completing  the  analogy  of  the  arrangement  of  the  arteries 
and  the  veins  of  this  region,  for  the  second  intercostal  and 
subcostal  veins  pass  to  the  dorsal  vein,  the  first  intercostal 
to  the  posterior  cervical.     The  blood  from  the  intercostal 
veins  therefore  passes  to  the  anterior  vena  cava.     The  in- 
tercostal nerves  are  derived  from  the  dorsal  intervertebral 
nerves,  each  of  which  on  emerging  from  the  intervebral 
foramen,  after  sending  fibres  to  and  receiving  fibres  from  the 
gangliated  cord  of  the  sympathetic,  sends  superior  branches 
to  longissimus  dorsi  and  the  other  structures  on  the  back, 
while  its  inferior  branch  runs  between  the  ribs.     Those 
most  posteriorly  situated  are  continued  from  the  inferior 


3  88  OUTLINES    OP   EqUINE   ANATOMY. 

extremities  of  the  intercostal  spaces  over  the  external 
surface  of  transversalis  abdominis,  forming  remarkable 
parallel  white  cords  (falsely  termed  abdominal  ribs).  The 
most  ]3osterior  of  these  are  derived  from  the  lumbar 
nerves  which  resemble  the  dorsal,  but,  of  course,  do  not 
possess  intercostal  branches. 

The  THORAX  must  now  be  opened,  which  may  be  done 
by  cutting  through  the  superior  and  inferior  extremities  of 
the  ribs  from  the  second  to  about  the  twelfth  by  means  of 
a  saw,  and  removing  the  separated  portion  of  the  wall  of  the 
chest  by  cutting  through  the  first  and  twelfth  intercostal 
muscles.  The  pleura  or  serous  lining  membrane  of  the 
chest  is  thus  exposed,  and  since  it  is  very  transparent  we 
can  see  the  structures  it  covers  very  plainly  through  it. 
The  thorax  is  the  anterior  cavity  of  the  trunk.  It  is 
pyramidal  in  form,  its  apex  being  anteriorly  placed,  its 
base  cut  off  obliquely  from  below  upwards  posteriorly. 
Superiorly  it  is  bounded  by  the  under  surfaces  of  the^ 
bodies  of  the  dorsal  vertebrae,  which  centrally  form  a 
prominent  ridge,  which  anteriorly  from  the  sixth  vertebra 
is  bounded  on  either  side  by  a  prominent  fleshy  mass,  the- 
thoracic  ])ortion  of  longus  colli.  On  either  side  the  roof  of 
the  thorax  is  formed  by  the  arch  of  the  ribs,  while  the 
straighter  portion  of  them  passes  downwards  to  articulate 
with  the  sternum  through  the  medium  of  the  costal  carti- 
lages, thus  with  the  aid  of  the  intercostal  muscles  form- 
ing the  sides  of  the  thorax.  Its  floor  is  about  one  half- 
the  length  of  the  roof,  and  is  formed  of  the  sternum  with 
its  cartilages.  Its  apex  is  the  space  between  the  two  first 
ribs,  through  which  important  structures  pass,  i.  e.  longus 
colli  muscles  (2),  common  carotid,  axillary  (2),  vertebral 
(2),  inferior  cervical  (2),  external  pectoral  (2),  arteries  with 
the  corresponding  veins  (jugular  vein  corresponds  to 
carotid  artery),  trachea,  oesojDhagus,  pneumogastric,  recur- 
rent, phrenic,  gangliated  cord  of  sympathetic  nerves. 

The  base  of  the  thorax  is  formed  by  the  anterior,  coru 
vex,  surface  of  the  diaphragm,  the  thin  expanded  muscle 
which  separates  this  cavity  from  the  abdomen.     The 

DIAPHRAGM  presents  centrally  a  heart-shaped  tendi- 
nous portion,  the  fibres  of  which  are  much  interlaced,  and 
which,  on  the  right  side  by  separation  of  its  fibres,  forms 
the  foramen  dextrum,  by  passing  through  which  the 
posterior  vena  cava  gains  the  cavity  of  the  chest,  during 


THE    BACK.  189 

its  passage  receiving  blood  from  the  flat  plirenic  or  dia- 
phragmatic venous  sinuses.  From  the  outer  margin  of 
this  tendinous  portion  muscular  fibres  radiate  towards  the 
inner  surfaces  of  the  inferior  extremities  of  the  twelve 
posterior  ribs,  or  of  their  cartilages,  where  thej  become 
inserted  in  forming  digitations  with  transversalis  abdo- 
minis, and  towards  the  upper  surface  of  the  ensiform 
cartilage.  The  indentation  in  the  upper  part  of  the  tendon 
is  filled  bj  three  muscular  masses,  two  of  which  arise  from 
the  left,  the  third  from  the  right  side  of  the  tendon.  Between 
the  right  muscular  mass  and  the  central  one  is  foramen 
sinistrum,  through  which  the  oesophagus  and  the  pneumo- 
gastric  nerves  pass  in  their  course  from  the  thorax  into  the 
abdomen;  subsequently  these  two  masses  combine  and 
form  a  tendon,  the  right  crus,  which  becomes  attached  to 
the  inferior  vertebral  ligament  as  far  back  as  the  fifth 
lumbar  vertebra;  the  third  mass  terminates  in  a  much 
shorter  tendon  is  termed  the  left  crus  of  the  diaphragm, 
and  becomes  inserted  into  the  inferior  vertebral  ligament 
below  the  body  of  the  first  lumbar  vertebra.  Between  the 
right  and  left  crura  is  situated  hiatus  aorticus,  which 
admits  the  passage  of  the  thoracic  duct,  posterior  aorta,  and 
vena  azygos,  while  passing  through  this  opening  the  pos- 
terior aorta  gives  off  the  phrenic  artery  which  supplies  the 
crura  of  the  muscle.  That  portion  of  the  diaphragm  ex- 
tending from  the  spine  to  the  internal  surface  of  the  last 
rib  passes  over  the  anterior  part  of  the  inferior  surface 
of  the  psoas  muscles,  and  above  it  also  we  see  the  gan- 
gliated  cord  of  the  sympathetic  and  the  greater  and  lesser 
splanchnic  nerves  passing  on  either  side. 

The  chest  is  lined,  and  the  viscera  it  contains  covered 
by  the  pleura,  a  serous  membrane  arranged  in  such  a 
manner  as  to  form  two  sacs,  one  on  each  side  of  the 
cavity,  which  lie  together  along  the  middle  line  so  as  to 
form  a  septum  extending  in  an  antero-posterior  direction, 
consisting  of  two  adjacent  layers  of  pleura  in  some  parts 
in  close  apposition,  in  others  separated  by  the  interposi- 
tion of  important  structures,  but  postero-inferiorly  pre- 
senting numerous  perforations,  whereby  one  pleural  sac 
is  brought  into  communication  with  the  other.  This  is 
the  mediastinum,  and  extends  from  the  internal  surface 
of  the  two  first  ribs  to  the  central  line  of  the  diaphragm. 
■Centrally  it  contains  the  heart,  being  reflected  to  form 


190  OUTLINES    OF   EQUINE   ANATOMY. 

tlie  external  serous  layer  of  tlie  pericardium.  This  is  tlie 
'middle  onediastinum,  while  those  portions  anteriorly  and 
posteriorly  placed  to  the  heart  are  the  anterior  and  pos- 
terior mediastina.  The  anterior  mediastinum,  therefore, 
contains  the  following  structures ;  anterior  aorta  and  two 
arterise  innominatse  with  the  commencement  portion  of  the 
branches  given  off  by  them ;  the  anterior  vena  cava  with 
the  terminating  portions  of  some  of  its  component  veins  ; 
part  of  the  trachea  and  oesophagus,  pneumogastric,  phrenic, 
recurrent,  and  sympathetic  nerves  and  thoracic  duct,  and 
superiorly  the  terminating  portion  of  longi  colli  (right  and 
left)  ;  interiorly,  the  thymus  gland  or  its  remains.  The 
middle  mediaslinum  is  mainly  occupied  by  the  heart  en- 
closed in  the  pericardium,  and  superiorly  may  be  dis- 
tinguished the  large  vessels  which  it  receives  or  gives  off 
(including  vena  azygos,  which  it  receives  indirectly),  and 
which  serve  to  attach  it  to  the  under  surface  of  the  spine. 
Also  we  here  see  the  oesophagus  situated  on  the  right  side 
of  the  base  of  the  heart  ;  the  trachea  terminating  in 
bifurcating  to  form  the  right  and  left  bronchi,  and  the 
thoracic  duct  winding  from  the  right  to  the  left  side  towards 
its  termination.  From  the  supero-lateral  parts  of  this 
mediastinum  also  we  find  the  visceral  pleura  projecting,  to 
surround  the  right  and  left  lungs.  Through  this  medias- 
tinum also  the  two  pneumogastrics,  the  left  recurrent  and 
the  two  phrenic  nerves,  run.  The  posterior  mediastinu^l 
is  much  longer  suj)eriorly  than  inferiorly,  and  is  j^erforated 
inferiorly.  At  its  superior  part  are  three  vessels  which, 
after  passing  through  or  while  going  to  hiatus  aorticus, 
course  along  the  under  surface  of  the  spine.  On  the 
right  side  vena  azygos,  on  the  left  the  posterior  aorta ; 
centrally  the  thoracic  duct  which  seems  to  be  simply  a 
space  between  the  two,  so  thin  and  uncoloured  are  its 
walls.  Lower  down  the  oesophagus  accompanied  by  the 
two  pneumogastric  nerves  courses  through  this  medias- 
tinum towards  the  foramen  sinistrum,  with  it  also  runs  the 
left  lohrenic  nerve.  The  right  2?lirenic  nerve  with  posterior 
vena  cava  passes  through  a  sj^ecial  fold  of  pleura  situated 
between  two  lobes  of  the  right  lung. 

We  have  now  examined  the  pleura  and  have  seen  that 
it  is  divided  into  a  parietal  and  a  visceral  portion  ;  the 
former  consists  of  the  costal  and  phrenic,  the  latter  of  the 
pulmonary  and  raediastinal  portions.     In  health  these  parts 


THE    BACK.  191 

lie  in  contact  with  one  another,  the  pleural  sac  being  prac- 
tically obliterated,  only  producing  sufficient  serous  fluid  to 
obviate  any  friction  which  might  be  caused  b}^  the  move- 
ments of  the  parts.  Thus  any  enlargement  of  the  thorax 
causes  distension  of  the  lungs,  for  air  rushes  in  through  the 
trachea  to  fill  up  the  extra  space.  In  disease  frequently 
large  quantities  of  fluid  collect  here,  and  membranes  are 
formed  which,  by  causing  union  of  the  parietal  to  the 
visceral  portion  of  the  pleura,  lead  to  obliteration  of  the 
sac,  placing  the  animal  in  a  condition  analagous  to  that 
normally  obtaining  in  birds,  which  class  of  animals  is 
characterised  by  absence  of  pleura.  Where  the  parietal 
comes  into  connection  with  the  visceral  pleura  the  bronchi 
and  pulmonary  arteries  enter  the  lung,  and  the  pulmonary 
vems  emerge  from  it.  This  is  termed  the  root  of  the  lung". 
(The  root  of  the  left  side  is  attached  to  the  base  of  the 
heart.) 

The  trachea  breaks  up  into  two  bronchi.  The  right  is  the 
largest,  and  passes  to  the  right,  being  crossed  by  the  oeso- 
phagus. It  is  larger  than  the  left,  and  breaks  up  into  three 
parts  on  joining  the  right  lung ;  for  this  lung  is  larger 
than  the  left,  which  is  deficient  centrally  to  allow  room 
for  the  movement  of  the  apex  of  the  heart  in  a  direction 
upwards  and  to  the  left.  And  it  has  also  three  lobes,  while  the 
left  has  hut  two.  Between  its  middle  and  posterior  lobes  is 
situated  the  pleural  fold  for  the  posterior  vena  cava  and 
right  phrenic  nerve. 

The  bronchi  are  composed  of  complete  cartilaginous 
rings ;  they  divide  and  subdivide  in  the  substance  of  the 
lung,  and  the  cartilaginous  rings  become  thinner  and  divided 
into  several  small  portions  until  at  last  they  disappear ;  so 
in  the  smaller  bronchial  tubes  the  walls  are  membranous. 
Between  the  cartilaginous  rings  and  the  mucous  membrane 
are  situated  unstriated  muscular  fibres,  extending  in  a  cir- 
cular manner  comi^letely  round  the  tubes.  The  mucous 
membrane  itself  at  first,  like  that  of  the  trachea  with  which 
it  is  directly  continuous,  presents  columnar  ciliated  ej^i- 
thelium ;  but  in  the  smallest  bronchi  the  cells  assume  the 
tessellated  character  and  lose  their  ciliae,  so  that  here  it 
resembles  serous  membrane.  These  minute  bronchial  tubes 
terminate  in  the  air-cells  or  infundibula,  elongated  spaces 
with  saculated  ivalls  (air-sacs),  on  the  external  surface  of 
which  the  pulmonary  capillaries  are  distributed  in  so  close 


192  OUTLINES    OF   EQUINE    ANATOMY. 

a  network  that  the  meshes  are  not  so  large  as  the  vessels 
themselves  ;  and  to  bring  about  more  complete  aeration  of 
the  blood,  in  consequence  of  the  close  connection  of  the 
air-cells,  each  layer  of  capillaries  is  in  apposition  on  both  sur- 
faces with  the  thin  wall  of  an  air-cell,  which  has  here  become 
but  little  more  than  a  layer  of  basement  membrane  covered 
by  simple  tessellated  epithelium.  Thus  the  air  and  the 
blood  do  not  come  into  direct  contact,  but  interchange  of 
gases  takes  place  by  the  process  of  osmosis  through  the 
layers  of  epithelial  cells  of  the  air- sacs  and  of  the  capillaries 
and  their  respective  basement  membranes.  Two  arteries 
pass  to  the  lungs ;  of  these  the  bronchial,  derived  by  a 
root  which  it  shares  with  the  oesophageal,  from  the  posterior 
aorta  or  from  the  sixth  intercostal  artery,  is  the  nutrient 
vessel  of  the  organ ;  while  the  pulmonary  artery  is  the  func- 
tional vessel,  which  brings  that  •  blood  which  requires  aera- 
tion (and  which  will  be  shortly  noticed) .  The  blood  obtained 
•through  these  two  vessels  seems  to  become  mixed  in  the 
capillaries,  and  returns  either  by  the  pulmonary  veins  into 
the  heart,  or  by  the  bronchial  veins  into  vena  azygos,  and 
so  indirectly  into  the  anterior  vena  cava.  The  lym])liatics 
of  the  lungs  are  numerous  and  converge  towards  certain 
bronchial  lymphatic  glands,  which  may  be  found  as  grey 
nodular  bodies  at  the  root  of  the  lungs.  The  nerves  are 
the  pneumogastric  and  the  sympathetic,  which  intermix 
their  fibres  intimately  in  forming  the  bronchial  plexus  at 
the  root  of  the  lung.  All  these  structures  are  united 
together  by  areolar  tissue,  to  which  the  term  jpare7ichyma 
is  applied;  but  this  term  is  very  indefinite,  sometimes 
being  used  to  indicate  the  whole  lung-tissue  as  opposed  to 
the  pleura,  its  use  therefore  should  be  discontinued.  If 
we  now  remove  the  exposed  lung  by  cutting  through  its 
root  we  shall  see  the  HEART,  in  situ.  It  is  enclosed  in  a 
dense  membrane,  the  pericardium,  and  presents  a  base  and 
an  apex  ;  and  to  its  base,  which  is  superiorly  placed,  vessels 
from  above,  from  behind,  and  from  before,  are  attached, 
and  serve  to  sling  it  in  position.  The  pericardium  consists 
-essentially  of  a  membrane  composed  of  white  fibrous  tissue, 
fibrous  pericardium,  which  extends  from  these  vessels  at 
the  base  of  the  heart,  in  a  downward  direction,  to  become 
attached  to  the  upper  surface  of  the  ensiform  cartilage 
and  posterior  part  of  the  sternum.  It  is  covered  externally 
by  the  layers  of  pleura  forming  the  middle  mediastinum, 


THE    BACK.  193 

wMch  here  separate  to  accommodate  the  central  organ  of 
circulation.  Internally  it  presents  a  smooth  surface,  for  it 
is  lined  by  a  serous  membrane,  serous  pericardium,  which 
becomes  reflected  from  the  base  of  the  heart  in  a  downward 
direction  over  that  organ,  which  it  invests  as  far  as  the 
apex,  and  thus  forms  a  closed  sac,  pericardial  sac,  which 
sometimes  contains  a  little  serous  fluid,  and  allows  the 
frictionless  play  of  the  heart  on  the  inner  surface  of  the 
fibrous  pericardium,  whose  function  is  to  restrain  its 
excessive  action. 

If  we  have  opened  the  chest  on  the  right  side  we  shall 
now  be  able  to  see  the  large  veins  which  bring  the  blood 
from  the  various  parts  of  the  system  to  the  right  or  pulmo- 
nary division  of  the  heart. 

Anterior  vena  cava  commences  at  the  junction  of  the 
jugulars  between  the  two  first  ribs,  and  runs  directly  back- 
wards to  open  into  the  supero-anterior  part  of  the  right 
side  of  the  heart.  It  receives  branches  corresponding  to 
the  arteries  given  off  by  the  arteriae  innominatae, — axillary, 
vertebral,  dorsal,  internal  thoracic,  and  several  others, 
including 

Vena  azygos,  a  vein  which  commencing  underneath  the 
loins  from  the  most  anteriorly  placed  lumbar  veins,  runs 
in  a  forward  direction  underneath  the  spine  with  posterior 
aorta  and  the  thoracic  duct  (being  situated  most  to  the 
right  side).  About  oioposite  the  sixth  dorsal  vertebra  it 
dips  downwards  to  open  into  the  anterior  vena  cava  just  at 
its  termination,  and  during  its  course  receives  the  thirteen 
posterior  intercostal  veins  and  the  subcostal  branch  from 
the  dorsal ;  just  before  its  termination  it  receives  the  bron- 
chial veins.  In  consequence  of  its  situation  the  left  inter- 
costal veins  are  longer  than  the  right,  but  we  have  observed 
an  accessory  vena  azygos  on  the  left  side  of  the  spine  of  the 
ass.  The  anterior  vena  cava  at  its  termination  for  about 
three  inches  presents  red  muscular  fibres,  so  that  it  seems 
to  be  a  continuation  of  the  wall  of  the  auricle ;  thus,  in 
the  heart  removed  from  the  body,  it  may  be  distinguished 
from  the 

Posterior  vena  cava,  which,  on  emerging  into  the  thorax 
through  foramen  dextrum  enclosed  in  a  special  double  fold 
of  pleura  (with  the  right  phrenic  nerve),  runs  direct  to  the 
postero-superior  part  of  the  right  side  of  the  heart,  receiving 
no  vessels  in  its  course.     The  large  arteries  may  be  seen 

13 


194  OUTLINES    OF   EQUINE   ANATOMY. 

best  by  laving  open  tbe  left  side  of  the  thorax.  From  the 
base  of  the  heart,  between  the  two  ventricles  the  aorta 
passes  upwards  for  about  two  inches.  It  is  a  large  vessel 
with  stout  elastic  walls,  and  gives  off  the  coronary  arteries 
to  the  substance  of  the  heart  in  a  manner  which  will  be 
hereafter  described.  It  terminates  superiorly  in  the  anterior 
and  posterior  aortge.  The  terminal  portion  of  the  trachea 
lies  in  contact  with  its  right  side,  while  on  the  left  is  the 
pulmonaiy  artery  and  also  the  left  pneumogastric,  which  on 
passing  gives  off  its  recurrent  branch,  coursing  from  without 
inwards  around  the  posterior  margin  of  the  aorta,  and 
running  forwards  and  up  the  neck  to  supply  all  the  mus- 
cles of  the  larynx  with  the  exception  of  the  crico-thyroideus. 
In  consequence  of  this  arrangement  many  authorities  con- 
sider that  pressure  upon  this  nerve  durmg  the  heart's 
action,  by  producing  atrophy  of  the  muscles  it  supplies, 
causes  that  defect  in  respiration  termed  "  roaring." 

The  anterior  aorta,  after  coursing  for  a  short  distance 
through  the  anterior  mediastinum,  situated  below  and 
slightly  to  the  left  of  the  oesophagus  and  trachea,  terminates 
in  forming  the  two  arterise  innominatse,  the  right  of  which  is 
much  the  largest.  The  right  arteria  innominata  runs  in 
a  forward  direction  as  far  as  the  first  rib.  The  first  branch 
it  gives  off  superiorly  is  the  common  root  of  the  anterior 
dorsal  and lyosterior  cervical  arteries  (which  have  been  already 
noticed)  ;  around  this  from  without  inwards  the  recurrent 
branch  of  the  right  pneumogastric  winds  prior  to  passing 
uj)  the  neck.  These  vessels  arise  se23arately  on  the  left  side, 
for,  as  just  noticed,  the  recurrent  branch  of  that  side  winds 
round  the  aorta.  From  its  anterior  part  the  right  arteria 
innominata  gives  off  the  vertebral,  inferior  cervical,  axillary, 
and  common  carotid  arteries.  The  left  arteria  innominata 
gives  off  corresponding  branches  with  the  exception  of  the 
common  carotid,  and  from  the  inferior  part  of  each  vessel  is 
given  off  an  internal  thoracic  artery,  which  runs  along  the 
floor  of  the  thorax  at  the  lateral  j^art  of  the  superior  sur- 
face of  the  sternum.  It  gives  off  branches  outwards  to 
anastomose  with  the  external  pectoral  and  intercostal 
branches,  and  opposite  the  ensiform  cartilage  divides,  one 
of  its  branches  running  along  the  floor  of  the  abdomen  to 
anastomose  with  the  epigastric  artery  ;  the  other  along  the 
inferior  margins  of  the  false  ribs,  anastomoses  with  the 
terminal  extremities  of  the  posterior  intercostal  arteries, 


THE    BACK.  195 

and  sends  brandies  backwards  to  supply  tlie  abdominal 
muscles.  The  common  carotid  is  situated  below  the  trachea 
in  the  anterior  -psivt  of  the  thorax,  between  the  two  first 
ribs.  It  arises  from  the  right  arteria  innominata,  and  ter- 
minates in  bifurcating  to  form  the  right  and  left  carotid 
arteries. 

The  thoracic  duct  after  passing  through  hiatus  aorticus 
runs  forwards  situated  between  vena  azygos  on  the  right 
and  posterior  aorta  on  the  left.  Opposite,  about  the  sixth 
dorsal  vertebra,  it  swerves  to  the  left  side  and  passes  towards 
the  anterior  opening  of  the  thorax  to  terminate  in  the  left 
jugular  or  the  left  axillary  vein.  Its  walls  are  very  thin,  so 
that  its  course  is  demonstrable  but  with  difficulty.  Almost 
in  apposition  with  the  inner  surface  of  the  first  rib  we  may 
find  the  inferior  cervical  ganglion,  to  which  the  sympa- 
thetic cord  running  down  the  neck  passes,  after  presenting 
a  little  below  and  in  front  a  small  nodular  enlargement,  the 
middle  cervical  ganglion.  The  inferior  cervical  ganglion 
also  receives  a  band  of  nerve-fibres  coming  from  the  fora- 
mina in  the  transverse  processes  of  the  cervical  vertebrse, 
made  uj)  of  fibres  derived  from  the  cervical  nerves  while 
emerging  through  the  intervertebral  gaps  in  the  neck. 
From  this  ganglion  backwards  extends  the  gangliated  cord, 
running  first  against  the  lateral  part  of  the  longus  colli 
muscle,  then  at  the  suj)ero-lateral  part  of  the  thorax  against 
the  heads  of  the  ribs,  having  a  ganglion  opposite  each 
vertebra  and  being  visible  through  the  pleura  costalis,  by 
which  only  it  is  covered.  Each  ganglion  receives  fibres 
through  the  nearest  intervertebral  gap  from  the  spinal  cord, 
and  sends  fibres  to  the  neighbouring  intercostal  nerves 
From  the  thirteen  or  fourteen  posterior  ganglia  fibres 
are  given  off  which  combine  to  form  the  greater  splanchnic 
nerve,  with  difficulty  separable  from  the  gangliated  cord  as 
it  runs  backwards,  and  passes  above  the  diaphragm  with 
the  psoas  muscles  to  reach  the  semilunar  ganglion  in  the 
antero-superior  part  of  the  abdomen,  some  of  its  fibres  run- 
ning directly  to  the  kidney.  The  lesser  splanchnic  nerve 
arises  from  the  two  or  three  posterior  dorsal  ganglia,  and 
accompanies  the  greater  nerve,  terminating  in  a  similar 
manner.  The  inferior  ganglion  gives  off  fibres  which  run 
downwards  to  assist  the  pneumogastric  in  forming  the  car- 
diac i^lexus  at  the  base  of  the  heart,  and  the  i^ulmonary  at  the 
root  of  the  lungs.     These  plexuses  have  communication  with 


196  OUTLINES    OF   EQUINE   ANATOMY. 

the  phrenic  nerve,  whicli  arises  in  the  neck  from  branches 
of  the  third,  fourth,  and  fifth  cervical  nerves,  commnni- 
cating  with  the  axillary  plexus,  and  runs  backwards  over 
the  base  of  the  heart  to  the  diaphragm,  that  of  the  left  side 
passing  through  the  posterior  mediastinum,  the  right 
phrenic  nerve  accompanying  the  posterior  vena  cava  in  its 
special  fold  of  pleura. 

We  can  now,  by  division  of  the  above-described  vessels, 
remove  the  heart  from  the  thorax.  We  find  that  it  is  a 
hollow  muscular  organ,  cone-shaped,  with  its  base  upwards, 
having  its  apex  directed  downwards  and  backwards.  It  is 
covered  by  the  visceral  layer  of  the  serous  pericardium, 
which  gives  it  a  glistening  appearance,  and  through  which 
may  be  seen  the  furrows  on  the  surface  which  mark  its 
division  into  several  cavities.  Of  these  we  see  one  running 
downwards  on  each  side,  ventricular  furrow,  one^running 
horizontally  around  the  base  of  the  heart,  auriculo-ven- 
tricular  furrow.  These  contain  the  vessels  of  the  organ 
with  nerves  embedded  in  a  quantity  of  fat.  The  two 
ventricular  furrows  do  not  reach  the  apex  of  the  organ, 
but  meet  on  the  right  side  a  little  above  that  point. 

The  heart  is  divided  into  two  sides ;  7igM  or  imlmonary 
heart,  left  or  systemic  heart.  In  the  foetus  these  sides  com- 
municate by  the  foramen  ovale,  which  pierces  the  auricular 
septum,  being  partially  closed  by  a  valvular  arrangement 
of  the  lining  membrane  of  the  heart ;  but  in  the  adult, 
under  normal  conditions,  this  becomes  impervious,  being 
still  recognisable  on  the  right  side  of  the  septum  as  a  light 
circular  spot,  fossa  ovalis,  surrounded  by  a  prominent  elastic 
ring,  annulus  ovalis.  Thus,  after  birth  in  mammalia,  the 
two  sides  are  distinct ;  each  side  consists  of  two  cavities — 
an  auricle  superiorly,  a  ventricle  inferiorly.  The  heart  is 
lined  by  serous  membrane,  endocardium,  which  is  con- 
tinuous with  the  serous  membrane  lining  the  large  vessels, 
which  run  to  or  from  its  cavities.  On  the  left  side,  espe- 
cially in  the  auricle,  we  find  a  layer  of  yellow  elastic  tissue 
between  the  muscular  structure  and  endocardium.  The 
hasement  structure  of  the  heart  is  situated  at  the  point  of 
junction  of  the  four  cavities.  Here  we  find  a  firm,  irregular- 
shaped  piece  of  fibro-cartilaginous  substance,  which  in  the 
ox  is  always,  in  the  horse  occasionally,  ossified ;  from  this 
run  three  yellow  elastic  rings ;  one  to  the  right  side,  cir- 
cumscribing the  right  auriculo -ventricular  opening ;  another 


THE   BACK.  197 

backwards  and  slightly  to  the  left,  surrounding  the  left 
auriculo-ventricular  opening ;  the  third  to  the  left  slightly 
forwards,  from  which  superiorly  the  elastic  layer  of  the 
aorta  commences  ;  while  outwardly  it  is  continued  to  form 
a  ring  for  the  commencement  of   the  pulmonary  artery 
(this  bemg  the  weakest  of  them  all).     To  these  rings  is 
attached  the  muscular  structure  of  the  heart,  consisting  of 
fibres  all  arranged  in  a  more  or  less  oblique  manner.    Each 
cavity  possesses  fibres   peculiar  to   itself,  while  the   two 
auricles  are  connected  together  by  common  fibres,  and  the 
two  ventricles  also    by  common  fibres,  the  auricles  thus 
being  separable  from   the  ventricles  without  division  of 
muscular  fibre.     Thus  the  auricles  first  contract  together 
(synchronously),  then  the  ventricles  contract  simultaneously. 
The  muscular  walls  of  the  heart  are  smooth  externally, 
but  present  ^prominences  and  depressions  internally.     The 
right  auricle  is  situated  at  the  supero -anterior  part  of  the 
heart.     It  has  thin  walls,  which  collapse  when  the  cavity  is 
empty,  and  is  divided  into  two  parts,  sinus  and  apiJendix. 
It  is  termed  auricle  from  the  likeness  of  the  corresponding 
part  in  the  human  subject  to  a  dog's  ear ;  in  the  horse  the 
appendix  portion  assumes  this  figure,  and  is  inclined  to 
the  left  side,  where  it  terminates  in  a  point.     The  inner 
surface  of  this  part  presents  prominences  of  muscular  sub- 
stance arranged  in  a  reticulated  manner,  musculi i^ectinati, 
separated  by  dej^ressions,  foramina  Thehesii,  into  the  latter 
small  blood-vessels  are  supposed  to  open.  The  sinus  portion 
presents  five    openings.      At    its    supero-anterior   part    it 
receives   the    anterior  vena   cava,   with   which   vessel  its 
muscular  walls  are  structurally  continuous.    At  its  supero- 
posterior  part  the  posterior  vena  cava,  below  which  is  the 
double  opening  of  the  cardiac  or  coronary  veins.  The  walls 
of  the  sinus  present  but  few  muscular  prominences  ;  a  broad 
ridge  separates  the  opening  of  the  anterior  from  that  of  the 
posterior  vena  cava,  this  is  tuherculum  Loweri ;  below  it  may 
be  seen  the  remains  of  the  foramen  ovale  (fossa  ovalis  and 
annulus  ovalis).  In  the  human  subject  the  anterior  margin 
of  this  opening  presents  the  crescent-shaped  Eustachian 
valve  ;  we  have  not  seen  it  in  the  ass.     Between  the  coro- 
nary opening  and  the  termination  of  posterior  vena  cava  is 
a  thin  double  layer  of  endocardium,  with  a  small  quantity 
of  muscular  structure  intervening,  the  valve  of  Thehesius. 
The  inferior  part  of  the  auricle  presents  the  right  auriculo- 


198  OUTLINES    OP   EQUINE   ANATOMY. 

ventricular  opening,  consisting  of  a  smTonnding  fibrous 
ring,  from  whicli  hang  three  flaps,  composed  of  double 
layers  of  endocardmm  (the  serous  membrane  lining  the 
heart,  which  resembles  the  internal  coat  of  blood-vessels), 
which  serve  to  regulate  the  passage  of  the  blood  from  one 
cavity  to  the  other.  They  are  triangular  in  shape,  having 
their  outer  boundary  attached  to  the  circular  fibrous  ring, 
with  its  terminating  angles  confluent  with  the  other  two 
sides  which  form  the  free  margin  to  which  powerful  fibrous 
cords  (cliordce  tendinece)  are  attached.  These  chordae  ten- 
dinese  nin  to  large  projections  from  the  inner  surface  of 
the  muscular  wall  of  the  ventricle,  which  receive  the 
special  name  musculi  loapillares ;  they  are  three  in  number, 
one  projecting  from  the  outer  wall,  two  from  the  septum 
ventriculorum.  From  one  musculus  papillaris  chordae  ten- 
dinese  run  to  each  of  the  three  flaps  of  the  tricuspid  valve. 
The  wall  of  the  right  ventricle  is  thicker  than  that  of 
the  auricle,  and  presents  on  its  internal  surface  three 
forms  of  muscular  prominences  (carnese  columnae).  The 
mnsculi  impillares,  having  one  end  free,  constitute  the 
first  set;  the  moderator  lands  run  from  one  side  of  the 
cavity  to  the  other,  often  consist  simply  of  yellow  elastic 
tissue  covered  by  serous  membrane,  they  form  the  second  ; 
while  the  third  or  true  carnece  columnce  are  attached  by 
both  ends  and  by  one  margin,  thus  resembling  the  musculi 
pectinati  of  the  auricle.  The  right  ventricle  does  not 
extend  to  the  apex  of  the  heart,  which  is  wholly  formed  by 
the  left,  but  superiorly  it  forms  a  funnel-shaped  cavity 
(termed  conus  arteriosus),  behind  the  posterior  flap  of  the 
tricuspid  valve,  from  the  upper  extremity  of  which  the 
pulmonary  artery  commences.  The  communication  of  the 
ventricle  with  this  vessel  is  guarded  by  three  crescentic 
flaps  which  constitute  the  semilunar pidmonary  valves.  They 
have  a  free  and  an  attached  margin.  The  free  margin 
centrally  presents  a  point  on  which  we  sometimes  see  a 
small  nodule  {corpusculum  arantii),  which  serves  to  ensure 
complete  closure  of  the  opening  by  the  valves.  The 
attached  margin  is  continuous  with  the  pulmonary  fibrous 
ring  and  its  extremities  meet  the  other  flaps.  The 
pulmonary  artery  runs  backwards  and  in  passing  under 
the  posterior  aorta  is  connected  to  it  by  an  imi)ervious  cord, 
the  remains  of  the  ductus  arteriosus  of  the  foetus.  After  this 
it  bifurcates,  its  larger  division  passing  to  the  right  lung, 


THE    BACK.  199 

its  smaller  to  tlie  left.  On  examining  tlie  inner  surface  of 
this  vessel  three  saccular  dilatations  (sinus  Valsalvce)  of  its 
walls  may  be  noticed  behind  the  valves,  serving  to  accom- 
modate them  during  the  rush  of  blood  from  the  ventricle, 
and  to  allow  blood  to  collect  behind  the  flaps  in  sufficient 
quantity  when  this  rush  ceases  to  throw  the  valves  into 
position  and  thus  prevent  regurgitation  of  blood.  The 
pulmonary  arteries  divide  and  subdivide  in  the  lungs, 
and  finally  terminate  in  capillaries  in  which  the  blood  is 
oxygenated,  and  from  which  it  is  carried  by  the  pulmonary 
veins  to  the  left  auricle  of  the  heart.  The  pulmonary 
veins  unite  and  reunite  until  by  (generally)  four  openings 
they  pour  their  contents  into  the  heart ;  they  never  leave 
the  lung  substance,  for  it  is  here  also  attached  to  the  heart 
substance.  These  veins  have  no  valves.  The  left  auricle 
very  much  resembles  the  right,  from  which,  however,  it 
differs  in  the  greater  amount  of  yellow  elastic  tissue  lining 
it,  and  in  presenting  more  marked  musculi  pectinati  and 
foramina  Thebesii,but  no  fossa  ovalis,annulus  ovalis,  tuber- 
crum  Loweri,  or  Thebesian  valve.  Its  auriculo -ventricular 
opening  too  is  guarded  by  a  stout  valve  consisting  of  but 
two  flaps,  the  hicuspid  or  mitral  valve.  It  leads  into  the 
left  ventricle,  similar  in  structure  and  figure  to  the  right 
ventricle,  but  with  only  two  musculi  papillares,  both  of 
which  are  attached  to  the  outer  wall  of  the  cavity.  Its 
moderator  bands  generally  contain  muscular  fibres,  and  its 
walls  consist  of  very  thick  muscular  substance.  This  com- 
partment, however,  at  the  extreme  inferior  part,  where  it 
alone  forms  the  apex  of  the  heart,  consists  of  little  more 
than  a  double  layer  of  serous  membrane,  the  endo- 
cardium lying  in  contact  with  the  pericardium.  The  thick- 
ness of  the  muscular  wall  is  related  to  the  force  required 
in  driving  the  blood  through  the  system  when  the  elasticity 
of  the  coats  of  many  large  and  strong  vessels  has  to  be 
temporarily  counteracted.  The  blood  from  this  cavity 
passes  in  an  upward  direction  into  the  aorta,  which  is 
situated  on  the  right  side  of  the  pulmonary  artery,  to 
which  one  of  its  primary  divisions  (posterior  aorta)  is 
connected  by  an  elastic  ligament.  The  opening  into  this 
vessel,  like  that  of  the  pulmonary  artery,  presents  semi- 
lunar  valves,  but  they  are  larger,  stronger,  and  present 
more  marked  corpora  arantii ;  while  the  sinus  Valsalvse 
into  which  they  fit  are  deeper  than  those  of  the  pulmonary 


200  OUTLINES    or   EQUINE   ANATOMY. 

artery,  so  that  tlie  vessel  is  largest  and  its  walls  thinnest 
and  most  liable  to  rupture  here.  From  the  posterior  and 
also  from  the  internal  sinus  Valsalvse  a  coronary  artery 
arises,  going  to  supply  the  substance  of  the  heart.  The  left 
coronary  artery,  the  shortest,  runs  directly  down  the  left 
ventricular  furrow,  and  its  terminal  branches  anastomose 
with  those  of  the  right  at  the  point  of  union  of  the  two 
ventricular  furrows.  It  gives  off  a  branch  in  a  posterior 
direction  which  passes  in  the  posterior  auriculo -ventricular 
furrow  to  the  vessel  of  the  right  side.  The  right  coronary 
artery,  after  winding  through  the  anterior  auriculo -ventri- 
cular furrow,  meets  the  posterior  branch  of  the  left  artery 
and  then  runs  down  the  right  ventricular  furrow  to  meet 
the  left  artery  at  the  inferior  extremity.  The  blood  from 
the  heart  is  returned  by  the  coronary  or  cardiac  veins, 
of  which  the  left  is  the  longest ;  they  terminate  almost 
by  a  common  opening  in  the  right  auricle  as  already 
described. 

The  heart  is  supplied  with  nerve  power  from  three 
sources :  By  the  ^neumogastric  and  gangliated  cord  of  the 
symjMtlietic  through  the  medium  of  the  cardiac  plexus,  and 
by  small  symjKitlietic  ganglia  emhedded  in  its  substance.  The 
latter  endow  it  with  its  regularity  of  contraction  (rhythmic 
action),  the  pneumogastric  serves  to  restrain,  the  glan- 
gliated  cord  of  the  sympathetic  to  stimulate  its  action. 

The  muscular  fibres  of  the  heart  are  involuntary  ;  they 
nevertheless  present  slight  striation  and  a  modena  red 
colour,  similar  to  that  of  voluntary  muscle.  They  differ 
from  the  latter,  however,  in  the  imperfection  of  their 
striation,  in  the  absence  of  a  sarcolemmatous  sheath,  and 
in  frequent  anastomosis  of  the  constituent  fibrillse. 

In  the  infero-anterior  part  of  the  thorax,  at  the  lower 
part  of  the  anterior  mediastinum,  especially  developed  in 
the  foetus,  in  whom  it  extends  a  short  way  up  the  neck,  is 
the  thymus  gland,  a  body  resembling  a  salivary  gland  in 
appearance,  and  pouring  the  product  of  its  lobules  into  a 
central  cavity,  from  which,  as  there  is  no  duct,  it  seems  to 
be  reabsorbed.  It  is  a  vascular  gland,  and  is  the  true 
"  sweetbread." 


THE   POKE    EXTREMITY.  201 


.  PAUT  VII.— SPECIAL  ANATOMY. 

The  Fore  Extremity. 

The  skin  having  been  dissected  back  from  the  withers 
(a  work  rendered  easy  by  the  primary  incisions  on  either 
side)  down  to  a  little  below  the  elbow- joint,  the  panniculus 
is  shown  extending  over  the  limb  on  the  outside  as  far  as 
this  joint,  becoming  indirectly  attached  to  the  spine  of 
the  scapula,  the  point  of  the  shoulder,  the  humeral  ridge, 
&c.  Anteriorly  it  is  somewhat  intimately  connected  with 
levator  humeri,  posteriorly  it  covers  the  muscles  of  the 
shoulder,  and  dorsal  trapezius,  and  extends  on  to  the  lateral 
part  of  the  thorax.  From  the  lateral  parts  of  the  thorax 
some  fibres  of  panniculus  run  forwards  to  the  internal 
surface  of  the  shoulder.  The  panniculus  having  been  re- 
moved, levator  humeri  must  be  traced  in  its  attachments, 
to  the  spine  of  the  scapula  (blending  with  trapezius),  the 
external  ridge  of  the  humerus,  with  the  fibrous  band  run- 
ning downwards  from  it,  and  the  antero- inferior  part  of  the 
humerus.  The  latter  attachment  being  also  that  of  pec- 
toralis  transversus,  which  will  be  found  running  from  the 
under  surface  of  the  sternum  to  this  attachment,  and  by 
a  broader  part  (almost  separated  from  the  former)  to  the 
faschia  covering  the  inner  surface  of  the  arm.  By  divi- 
sion of  levator  humeri  along  the  anterior  margin  of  the 
scapula,  pectoralis  anticus  is  exposed ;  it  is  a  triangular 
elongated  muscle  arising  from  the  lateral  part  of  the  cari- 
niform  cartilage  and  from  the  external  surface  of  the  an- 
terior sterno-costal  cartilages  and  muscles,  and  running 
along  the  front  of  the  shoulder,  passing  over  pectoralis 
magnus  and  growing  thinner  superiorly  to  blend  with  the 
faschia  covering  antea  spinatus  and  to  reach  the  spine  of 
the  scapula.  Between  this  muscle  and  those  of  the  neck 
is  situated  a  quantity  of  loose  cellular  tissue  in  which 
much  fat  and  the  prescapular  lymphatic  glands  are  situ- 
ated.    The  subscapulo-hyoideus  muscle  runs  on  the  inner 


20.-^  OUTLINES   OF   EQUINE   ANATOMY. 

side  of  pectoralis  anticus,  forming  a  broad  muscular  layer 
attached  to  the  tendinous  aponeurosis  of  subscapularis  ; 
in  proceeding  up  the  neck  about  the  middle  third  this 
muscle  becomes  intimately  connected  with  the  internal 
surface  of  levator  humeri,  so  that  these  muscles  are  not 
easily  separable;  it  subsequently  passes  between  the  jugular 
vein  and  the  carotid  artery  to  its  insertion  into  the  hyoid 
bone. 

The  muscles  connecting  the  fore  limb  to  the  various 
neighbouring  parts  must  now  be  divided  (reference 
should  be  made  to  the  several  regions  under  the  heads  of 
which  their  attachments  are  described),  and  the  external 
scapular  miiscles  exposed,  these  are — 

Antea  spinatus,  running  from  the  anterior  dorsal  fossa 
of  the  scapula,  by  a  rounded  prominent  border  clothing 
the  major  portion  of  the  anterior  costa  of  that  bone  and 
becoming  attached  to  a  ligament,  which  runs  from  here  to 
the  coracoid  process,  between  which  and  the  bone  pass  the 
dorsal  scapular  vessels  and  nerves.  Inf eriorly  it  bifurcates 
and  with  pectoralis  magnus  becomes  inserted  into  the  ex- 
ternal and  internal  tubercles  on  the  anterior  part  of  the 
humerus  ;  the  surface  between  the  two  heads  is  lined  by  a 
tendinous  theca  or  sheath,  which  is  reflected  on  the  middle 
tubercle  of  the  bone  to  facilitate  the  gliding  of  the  carti- 
laginous superior  extremity  of 

Flexor  brachii  or  coraco-radialis,  which  having  arisen 
by  a  strong  tendon  from  the  coracoid  process  of  the  scapula, 
after  passing  through  this  sheath,  where  its  tendon  is  in- 
dented to  fit  upon  the  middle  tubercle,  runs  down  the  front 
of  the  humerus  inclined  to  the  inner  side,  forming  a  pro- 
minent muscular  cord  which  sends  a  strong  band  of  white 
fibrous  tissue  downwards  to  extensor  metacarpi  magnus, 
and  becomes  inserted  into  the  roughened  spot  previously 
noticed  as  situated  at  the  supero-internal  part  of  the  an- 
terior surface  of  the  radius  and  into  the  capsular  ligament 
of  the  elbow-joint;  at  the  antero-superior  part  of  its  tendon 
we  see  some  muscular  fibres. 

Postea  spinatus  is  to  be  found  in  the  posterior  fossa 
of  the  dorsum  of  the  scapula,  which  it  occupies  for 
its  superior  two  thirds  ;  separating  below  it  forms  two  ten- 
dons, one  of  which  is  attached  to  the  fourth  or  external 
tubercle  of  the  head  of  the  humerus,  while  the  other  plays 
over  this,  from  which  it  is  separated  by  a  synovial  bursa, 


THE   TORE    EXTREMITY.  203 

and  becomes  inserted  into  the  upper  part  of  tlie  ridge 
running  down  from  the  external  tubercle.  The  inner  sur- 
face of  the  first  head  is  attached  to  the  capsular  ligament 
of  the  shoulder- joint. 

Teres  externus  arises  from  faschia  which  covers  postea 
spinatus  and  extends  as  far  forwards  as  the  spine  of  the 
scapula,  also  from  the  superior  part  of  the  posterior  costa 
of  the  scapula.  It  is  at  first  composed  of  two  layers,  but 
these  combine  inferiorly  to  become  inserted  into  the  lower 
part  of  the  humeral  ridge.  Between  this  tendon  and  the 
lower  tendon  of  postea  spinatus  the 

Scapulo-humeralis  externus  is  inserted,  after  passing 
over  the  capsular  ligament  of  the  shoulder-joint  and  becom- 
ing attached  to  it,  and  arising  from  a  roughened  ridge  at 
the  postero-external  part  of  the  neck  of  the  scapula  at  the 
lower  part  of  the  fossa  postea  spinatus  in  front  of  caput 
magnum,  extending  to  a  slight  extent  around  its  inferior 
extremity  to  its  posterior  surface.  By  removing  the  superior 
attachment  of  this  muscle,  we  generally  expose  a  branch 
from  the  posterior  scapular  artery  passing  through  the 
medullary  foramen  of  the  scapula. 

Underneath  the  above-named  muscles  to  the  posterior 
surface  of  the  humeral  ridge  the 

Caput  medium  of  the  triceps  extensor  brachii  is  attached. 
The  triceps  is  that  large  mass  of  muscle  which  fills  up  the 
triangular  space  between  the  scapula  and  the  humerus ; 
as  its  name  indicates,  it  consists  of  three  parts  or  heads, 
named  according  to  their  respective  sizes.  Caput  magnum 
is  attached  superiorly  along  the  major  portion  of  the  pos- 
terior costa  of  the  scapula,  not  extending,  however,  to 
the  extreme  inferior  part.  It  is  attached  to  the  cap- 
sular ligament  of  the  shoulder- joint  and  covers  scapulo- 
humeralis  posticus,  and  at  the  extreme  inferior  part  becomes 
large  and  thick,  and  internally  to  its  superior  attachment 
presents  a  groove  in  which  rests  the  teres  major  vel  in- 
ternus  ;  between  the  two  muscles  is  the  posterior  scapular 
artery  with  its  accompanying  vein  and  nerve.  It  is  a  branch 
of  the  axillary  artery  and  runs  upwards,  sending  branches 
to  the  muscles,  between  which  it  runs  to  subscapularis. 
The  fibres  of  this  head  converge,  and  run  towards  the  point 
of  the  ulna,  into  which  they  become  inserted  through  the 
medium  of  a  short  stout  tendon  which  passes  over  a  bursa 
prior  to  insertion.   Caput  medium  runs  from  the  posterior 


204  OUTLINES    OF   EQUINE   ANATOMY. 

part  of  the  humeral  ridge  to  be  attached  by  a  wide  inser- 
tion to  the  tendon  of  the  caput  magnum  and  to  the  outer 
surface  of  the  olecranon.  Caput  parvum  arises  from  the 
upper  part  of  the  internal  ridge  which  bounds  the  ole- 
cranian  fossa  of  the  humerus  and  passes  to  the  point  of  the 
ulna  and  to  the  internal  surface  of  its  olecranian  process. 
The  internal  surface  of  this  head  is  in  contact  with  the 
humeral  vessels  and  nerves  derived  from  the  axillary 
plexus;  also  above  with  the  humeral  attachments  of 

Teres  interims,  which  arises  from  the  superior  part  of 
the  posterior  costa  of  the  scapula,  is  externally  in  contact 
with  caput  magnum  as  above  described,  and  inferiorly 
terminates  by  a  tendon  common  also  to  latissimus  dorsi,  at 
a  roughened  spot  on  the  internal  surface  of  the  middle 
third  of  the  humerus  ;  over  this  tendon  the  humeral  artery 
and  vein  and  several  important  branches  of  the  axillary 
plexus  of  nerves  pass.  It  will  be  seen  that  this  muscle 
exactly  corresponds  in  its  course  to  the  teres  externus  on 
the  outside  of  the  limb.  To  the  latissimus  dorsi  over  its  in- 
ferior extremity  runs  the  external  thoracic  branch  of  artery. 

On  looking  at  the  external  surface  of  the  shoulder,  we 
see  that  the  venter  surface  of  the  scapula  is  covered  over 
its  inferior  two  thirds  by 

Subseapularis,  which  is  covered  by  faschia,  from  which 
subscapulo-hyoideus  arises.  Superiorly  it  presents  a  margin 
of  attachment  divided  into  three  projections,  whereby  it 
leaves  two  triangular  spaces  for  insertion  of  serratus 
magnus.  Inferiorly  it  becomes  more  narrow,  and  finally 
for  the  most  part  tendinous,  and  inserted  into  the  tubercle 
situated  on  the  inner  surface  of  the  head  of  the  humerus. 
The  anterior  margin  of  this  muscle  is  in  contact  with 
antea  spinatus,  which  here  presents  a  rounded  surface  apt 
to  be  mistaken  for  another  muscle  until  the  limb  is  turned 
over  ;  between  these  two  muscles,  above  the  coracoid  pro- 
cess, the  anterior  scapular  artery  (a  branch  of  the  axillary) 
passes  with  its  accompanying  vein  and  nerve. 

Attached  to  the  process  on  the  internal  surface  of  the 
coracoid  process  is  the  tendon  of 

Coraco-humeralis,  which,  emerging  from  between  the  two 
muscles,  passes  over  the  insertion  of  subscapularis,  over 
which  it  plays  through  the  medium  of  a  bursa,  then  breaks 
up  into  two  muscular  portions  which  go  to  be  attached,  the 
superior  one  to  the  internal  surface  of  the  superior  third  of 


THE    FORE    EXTREMITY.  205 

the  liumerus,  the  inferior  to  the  superior  part  of  the  inferior 
third  of  the  anterior  surface  of  that  bone.  Between  these 
two  heads  runs  a  branch  of  the  humeral  artery  (with  its 
vein  and  nerve)  to  supply  flexor  brachii.  The  axillary 
nerves  and  vessels  will  be  found  in  contact  with  the  upper 
part  of  this  muscle. 

Scapulo- ulnar  is  runs  from  the  posterior  angle  of  the 
scapula  with  caput  magnum,  and  covering  the  internal 
surface  of  the  posterior  part  of  the  triceps,  expands  below 
to  become  inserted  into  the  inner  surface  of  the  olecranon 
and  the  faschia  covering  the  internal  surface  of  the  arm, 
foi-ming  an  aponeurotic  expansion  which  extends  upwards 
to  blend  with  its  superior  attachment. 

By  removal  of  triceps  we  expose  two  muscles,  both  of 
which  are  attached  to  the  capsular  ligaments  of  the  joints 
with  which  they  respectively  are  in  contact. 

Scapulo-humeralis  posticus  consists  of  a  few  fleshy  fas- 
ciculi, which  run  from  immediately  behind  the  glenoid 
cavity  of  the  scapula,  emerging  from  within  the  attachment 
of  caput  magnum,  and  after  passing  over  and  becoming 
attached  to  the  capsular  ligament  of  the  shoulder- joint, 
dip  between  the  fibres  of  humeralis  externus  to  become 
inserted  to  the  extreme  postero- superior  part  of  the  hu- 
merus immediately  below  the  articular  cartilage  of  the  head. 

Anconeus  arises  from  the  superior  part  of  the  ridges 
which  bound  the  olecranian  fossa  of  the  humerus  (espe- 
cially from  the  outer),  becomes  attached  to  the  capsular 
ligament  of  the  elbow-joint,  which  extends  around  the 
articular  part  of  the  fossa,  and  becomes  inserted  into  the 
antero- superior,  inclined  to  the  outer  part  of  the  olecranon. 

Humeralis  externus  arises  from  the  posterior  part  of 
the  humerus  immediately  beneath  its  head,  where  it  covers 
scapulo-humeralis  posticus,  and  from  the  back  of  the  bone 
as  far  down  as  the  supra  -  condyloid  ridges.  It  winds 
around  the  external  surface  of  the  bone  in  a  spiral  fossa 
bounded  by  ridges  (with  the  spiral  nerve),  passes  beneath 
the  band  of  white  fibrous  tissue,  mixed  with  yellow  elastic, 
which  runs  from  the  inferior  extremity  of  the  humeral 
ridge  to  the  external  ridge  of  the  inferior  extremity  of  the 
humerus,  passes  between  flexor  brachii  and  extensor  meta- 
carpi  magnus  beneath  the  tendinous  band  connecting 
these  two  muscles,  and  having  become  attached  to  the 
anterior  part  of  the  capsular  ligament  of  the  elbow-joint, 


206  OUTLINES   OF   EQUINE   ANATOMY. 

forms  a  flat  tendon  whicli  passes  nnderneatli  tlie  inferior 
portion  of  tlie  internal  lateral  ligament,  where  it  is  lubri- 
cated with  synovia,  and  becomes  inserted  into  the  internal 
surface  of  the  head  of  the  radius  and  into  the  inner 
sharpened  border  of  the  ulna. 

Muscles  attached  to  the  capsular  ligament  of  the  sca- 
pulo -humeral  joint : 

Antea  spinatus,  postea  spinatus,  subscapularis,  scapulo- 
humerales  externus  and  posticus,  and  caput  magnum. 
Flexor  brachii  is  separated  from  it  by  a  quantity  of  fat 
and  its  bursa,  coraco-humeralis  by  the  subscapularis  ten- 
don and  a  bursa. 

The  axillary  artery  must  now  be  viewed  as  a  whole. 
It  commences  from  the  anterior  part  of  arteria  innominata 
within  the  chest,  and  takes  a  turn  around  the  anterior 
margin  of  the  first  rib  below  the  inferior  head  of  scalenus 
at  its  posterior  attachment.  It  thus  gains  the  external 
part  of  the  thorax  and  the  internal  surface  of  the  limb, 
so  that  on  raising  the  limb  after  division  of  the  pectoral 
muscles  we  see  this  vessel  with  its  corresponding  vein,  and 
the  axillary  plexus  of  nerves,  with  the  axillary  lymphatic 
glands  embedded  in  loose  cellular  tissue,  in  the  neighbour- 
hood of  the  shoulder- joint.  It  gives  off  arteria  dorsalis 
scapulse  (or  anterior  scapular  artery),  posterior  scapular 
(or  subscapular),  external  thoracic,  and  humeral  arteries, 
the  course  of  which  we  have  already  noticed;  also  the 
humeral  thoracic  which  runs  to  supply  pectoralis  magnus 
and  antea  spinatus  at  the  point  of  the  shoulder.  The 
humeral  artery  in  its  course  along  the  internal  surface  of 
the  humerus  gives  off  a  hrcmch  anteriorly,  which  passes 
hehveen  the  tivo  heads  of  coraco-humeralis  to  flexor  hrachii, 
a  large  branch  hackivards  to  tricejos  extensor  hrachii,^  and  a 
branch  inwards  opposite  the  superior  part  of  the  inferior 
third  of  the  bone,  which  pierces  its  substance  by  imssing 
through  the  medullary  foramen.  The  artery  then  passes  to 
the  anterior  margin  of  the  bone  and  breaks  up  into  the 
ulnar,  spiral,  and  radial  arteries.  The  ulnar  runs  back- 
wards, and  very  soon  breaks  up  to  form  a  number  of 
smaller  vessels,  which  all  run  to  structures  near  the  ole- 
cranon. The  spiral  passes  over  the  front  of  the  elbow- 
joint,  and  runs  down  the  anterior  surface  of  the  radius 
in  company  with  a  vein  and  nerve.  The  radial,  after 
passing  over  the  internal  surface  of  the  elbow -joint,  dips 


THE    PORE    EXTREMITY.  207 

underneatli  flexor  metacarpi  internus,  on  the  inner  sur- 
face of  which  it  runs,  in  company  with  an  artery,  vein, 
and  nerve,  as  far  as  the  knee,  sending  out  branches  to  the 
flexors  in  its  course,  even  to  fleccor  metacarpi  externus ;  the 
hranch  to  this  muscle  runs  through  the  arch  in  the  u7iion  of 
the  ulna  to  the  radius^  and  in  the  passage  gives  off  the  medul- 
lary artery  of  the  radius. 

The  axillary  plexus  of  nerves  is  formed  by  the  union  of 
nerve -fibres  from  the  three  posterior  cervical  and  the  first 
dorsal  intervertebral  nerves,  which  also  receive  a  branch 
from  the  sympathetic  system.  Emerging  between  the  long 
and  short  heads  of  scalenus,  the  plexus  is  thus  separated 
in  winding  around  the  first  rib  from  the  artery  and  vein  by 
the  lower  head  of  that  muscle.  From  this  point  collections 
of  fibres  pass  in  company  with  the  corresponding  arteries, 
thus  we  find  the  dorsalis  scapulce,  humeral  thoracic,  external 
thoracic,  and  subscapular  nerves,  which  differ  only  in  arrange- 
ment from  the  arteries  in  that  their  fibres  separate  before  ar- 
riving at  the  parts  which  they  supply,  and  become  thus  more 
diffused  over  its  surface.  lu  addition  to  these  the  axillary 
plexus  gives  off  the  ulnar,  spiral  and  radial  nerves,  for  we  find 
no  recognised  humeral  nerve.  The  radial  runs  with  the  artery 
of  the  same  name,  and  below  the  knee  forms  the  internal 
metacarpal  nerve  ;  it  gives  off  a  branch  which  runs  forwards 
with  the  spiral  artery  to  the  front  of  the  elbow -joint, 
where  it  meets  the  true  spiral  nerve,  which  ran  in  a  back- 
ward direction,  behind  the  humerus,  piercing  the  fleshy 
mass  of  the  shoulder  by  passing  between  caput  parvuni 
and  caput  magnum  to  gain  the  inferior  margin  of  hume- 
ralis  externus,  with  which  it  winds  round  the  external 
surface  of  the  bone,  gains  the  anterior  surface  of  the  joint, 
and  meets  the  artery,  with  which  it  runs  to  the  extensor 
muscles  and  the  skin  covering  the  front  of  the  limb.  The 
ulnar  nerve,  from  the  point  of  the  ulna,  sends  a  loiig  hranch 
down  behind  the  limb  underneath  ulnaris  accessorius,  which 
below  the  knee  becomes  the  external  metacarpal  nerve. 

Two  important  veins  are  to  be  found  in  the  region  of 
the  shoulder.  The  humeral  vein  receives  blood  from  the 
radial  and  ulnar  veins,  and  also  from  a  branch  which  runs 
to  it  from  just  in  front  of  the  termination  inferiorly  of 
flexor  brachii.  It  then  runs  up  the  limb  posteriorly 
placed  to  the  artery  and  terminates  in  the  axillary  vein, 
which  in  most  respects  resembles  the  artery  and  opens  into 


208  OUTLINES   OF   EQUINE   ANATOMY. 

tlie  anterior  vena  cava.  Along  tlie  internal  surface  of  the 
fore  limb,  in  the  living  animal,  we  may  see  a  large  vein 
running  upwards  along  the  subcutaneous  portion  of  the 
radius.  This  is  the  superficial  brachial,  cephalic,  or 
plat  vein,  from  which  blood  is  sometimes  extracted  by  the 
process  of  venesection  ;  at  the  insertion  of  flexor  brachii 
it  sends  a  branch  internally  to  that  muscle  to  join  the 
humeral  vein  as  above  mentioned,  but  the  main  portion 
runs  along  the  groove  between  this  muscle  and  extensor 
metacarpi  magnus,  and  proceeding  upwards  empties  its 
contents  into  the  jugular  vein ;  opposite  the  front  of  the 
elbow-joint  this  vessel  receives  the  spiral  vein.  Now  the 
skin  may  be  removed  from  the  internal  surface  of  the  arm ; 
this  may  be  done  by  an  incision  along  the  central  line  from 
the  elbow- joint  to  the  lower  part  of  the  knee,  through  the 
circular  horny  process  or  chestnut  found  opposite  the 
inferior  part  of  the  superior  third  of  the  radius,  and  dis- 
secting the  skin  backwards  and  forwards.  It  will  be 
advisable  also  to  remove  the  integuments  from  the  outer 
surface  of  the  limb  as  low  as  the  knee,  if  sufficient  time  is 
available  for  examination  of  both  aspects  of  the  arm  (other- 
wise the  white  fibrous  tissue  of  the  outside  will  become 
dry  and  hard  by  exposure  to  the  air).  Thus  the  aponeu- 
rotic expansion  of  pectoralis  transversus  and  panniculus  is 
exposed,  it  inferiorly  gradually  blends  with  the  ordinary 
subcutaneous  areolar  tissue.  By  division  of  it  we  bring  to 
view  the  faschia  of  the  arm,  a  dense  layer  of  white  fibrous 
tissue  running  round  the  back  of  the  limb  from  the  outer 
sharpened  border  of  the  ulna  to  the  inner  surface  of  the 
radius,  supero -internally  it  terminates  by  blending  with  the 
internal  lateral  ligament  of  the  elbow-joint,  and  by  becoming 
attached  to  the  point  of  the  ulna,  between  these  two  attach- 
ments it  receives  the  insertion  of  scapulo-ulnaris.  Inferiorly 
it  blends  with  the  annular  ligament  of  the  knee,  which  is 
nothing  more  than  a  thickening  of  this  faschia  in  conse- 
quence of  the  addition  to  its  substance  of  fibres,  some  of 
which  run  from  the  inner  surface  of  the  radius  just  above 
the  knee  to  trapezium,  others  from  the  inner  surface  of  the 
knee  obliquely  upwards  and  outwards.  From  the  internal 
surface  of  the  annular  ligament  of  the  knee  thick  fibrous 
bands  pass  to  enclose  the  tendons  situated  at  the  back  of 
the  knee-joint.  The  first  muscle  posteriorly  situated  to  the 
radius  is — 


THE    TORE    EXTREMITY.  209^ 

Flexor  metacarpi  internus.  It  arises  from  tlie  internal 
surface  of  the  inferior  extremity  of  the  humerus,  where  it 
is  attached  to  a  slightly  prominent  ridge,  j^asses  over  the 
caj)sular  ligament  of  the  elbow- joint,  to  which  it  is  firmly 
attached,  and  runs  downwards  along  the  internal  margin  of 
the  posterior  surface  of  the  radius  covering  the  radial  artery y 
vein,  and  nerve.  It  then  runs  through  a  synovial  sheath 
behind  the  knee,  and  becomes  inserted  into  the  head  of  the 
inner  small  metacarpal  bone.  This  sheath  is  strengthened  ex- 
ternally by  a  fibrous  band  reflected  from  the  internal  surface 
of  the  annular  ligament,  which  superiorly  blends  with  the 
stipe7'ior  siisiDensory  ligament,  a  dense  white  fibrous  tissue 
band  running  from  the  posterior  part  of  the  inferior  ex- 
tremity of  the  radius  to  the  perforans  and  the  perforatus 
tendons.  This  septum  is  broad  superiorly,  but  inferiorly 
grows  narrow,  and  separates  the  tendon  of  flexor  metacarpi 
internus  from  those  of  the  perforatus  and  the  perforans. 
Opposite  the  superior  part  of  this  reflection  a  small  branch 
runs  from  the  radial  artery  to  become  superficially  placed 
on  the  inner  surface  of  the  limb,  the  small  metacarpal, 
which  anastomoses  with  the  recurrent  branch  of  the  large 
metacarj^al,  and  gives  off  the  medullary  artery  of  the  large 
metacarpal  bone.  The  annular  ligament  of  the  knee 
terminates  below  in  a  definite  band  of  white  fibrous  tissue 
at  the  inferior  part  of  the  middle  third  of  the  internal 
surface  of  the  inner  small  metacarpal  bone  ;  between  this 
bandand  the  remainder  of  the  ligament  the  inyier metacarpal 
vein  passes  to  gain  the  cutaneous  surface  of  the  limb,  and 
from  it  the  superficial  radial  vein  arises,  which  passes 
upwards  to  the  superficial  brachial  vein. 

Flexor  metacarpi  medius  is  situated  posteriorly  to  flexor 
metacarpi  internus.  It  is  broad  superiorly,  where  we  see 
some  of  its  tendinous  fibres  running  transversely  from  the 
point  of  the  ulna  to  get  a  firm  insertion  into  the  capsular 
ligament  of  the  elbow-joint,  and  into  the  inferior  part  of 
the  ridge  running  upwards  from  the  inner  condyle  of  the 
humerus.  Under  this  part  run  the  ulnar  artery,  vein,  and 
nerve.  The  ulnar  nerve  proceeds  down  the  back  of  ih& 
limb  at  first  underneath  ulnaris  accessorius,  and  then  about 
opposite  the  inferior  part  of  the  middle  third  of  the  radius 
passes  under  the  tendon  of  that  muscle  to  gain  the  inner 
surface  of  flexor  metacarpi  externus.  The  postero-superior 
part  of  flexor  metacarpi  medius  blends  with  ulnaris  acces- 

14 


210  OUTLINES    OF   EQUINE   ANATOMY. 

sorius,  becoming  attaclied  firmly  to  tlie  posterior  surface  of 
the  superior  extremity  of  the  olecranon  ;  inferiorly  it  blends 
with  the  faschia  of  the  arm  and  with  flexor  metacarpi 
internus,  the  tendinous  band  so  formed  becoming  firmly 
attached  to  the  superior  margin  of  trapezium,  and  to  the 
annular  ligament  of  the  knee. 

Flexores  pedis  perforansand  perforatus. — Attached  to  the 
infero- posterior  part  of  the  ridge  running  upwards  from 
the  inner  condyle  of  the  humeiiis  and  to  the  capsular  liga- 
ment of  the  elbow-joint,  are  numerous  muscular  fasciculi, 
comprised  mainly  of  four  masses  which  run  down  the  pos- 
terior surface  of  the  radius  and  inferiorly  combine,  three 
of  them  forming  the  perforans  tendon,  the  other  the  per- 
foratus ;  the  first  is  triangular  in  shape,  being  concave  on 
its  posterior  surface  for  the  reception  of  the  second.  To 
the  inner  margin  of  each  tendon  runs  a  part  of  the  supe- 
rior suspensory  ligament,  that  to  perforatus  being  the 
widest  and  strongest.  Here  the  tendons  of  radialis  and 
nlnaris  accessorius  blend  with  that  of  perforans.  The 
tendons  of  perforans  and  perforatus  with  the  metacarpal 
artery,  vein,  and  nerves  run  together  in  a  synovial  sheath, 
separated  from  that  of  flexor  metacarpi  internus  by  a  fibrous 
layer  from  the  annular  ligament.  This  sheath  superiorly 
is  bounded  by  the  superior  suspensory  ligament,  extends 
downwards  for  about  four  inches,  terminating  inferiorly 
opposite  the  heads  of  the  small  metacarpal  bones,  where  it 
is  bounded  by  the  subcarpal  ligament,  a  diffused  layer  of 
ligamentous  fibres  which  arises  from  the  inferior  part  of 
the  annular  ligament,  where  it  immediately  invests  the  pos- 
terior surface  of  the  small  bones  of  the  knee,  and  runs 
mainly  to  the  perforans  tendon,  though  a  few  of  its  fibres 
run  on  either  side  of  that  tendon  to  perforatus.  Perforans 
is  said  to  form  a  sheath  for  perforatus  at  the  back  of  the 
knee,  this  is  hardly  correct ;  it  forms  the  anterior  part  of 
an  imperfect  sheath  which  is  laterally  composed  of  superior 
suspensory  ligament,  and  another  layer  of  the  annular 
ligament  of  the  knee,  but  between  the  two  tendons  is  a 
synovial  sheath,  which  on  the  outer  side  communicates  with 
the  former  sheath,  but  does  not  extend  so  far  inferiorly 

(by  one  and  a  haK  inches),  though  superiorly  it  extends  as 
far  up  as  the  superior  part  of  the  inferior  third  of  the 
radius.  We  must  temporarily  defer  the  examination  of  the 
xemaining  portion  of  these  tendons. 


THE    POKE   EXTREMITY.  211 

Radialis  accessorius  arises  from  the  posterior  surface  of 
the  middle  third  of  the  humerus  inclined  to  its  outer  side  ; 
its  fibres  become  inserted  into  the  perforans  tendon,  in 
blending  with  the  superior  suspensory  ligament  above  and 
"behind  the  knee. 

Ulnaris  accessorius  runs  to  the  same  insertion,  after 
arising  from  the  posterior  part  of  the  olecranon  in  common 
with  flexor  metacarpi  medius.  Its  muscular  portion  covers 
the  ulnar  nerve  and  is  covered  by  the  faschia  of   the  arm. 

On  examination  of  the  external  surface  of  the  arm  we 
find  that  the  faschia  of  the  arm  blends  anteriorly  with  the 
fibrous  band  of  extensor  metacarpi  magnus,  which  runs 
from  flexor  brachii.  Supero-externally  its  fibres  converge 
to  form  a  white  tendinous  band  (which  contains  some  yel- 
low elastic  fibres,  and  to  which  levator  humeri  and  pectoralis 
transversus  are  attached).  This,  superiorly,  is  firmly  at- 
tached to  the  inferior  extremity  of  the  ridge  running  down- 
wards from  the  external  tubercle  of  the  humerus,  passes 
over  and  binds  down  humeralis  externus  in  its  course  over 
the  external  surface  of  the  humerus,  and  posteriorly  runs 
to  become  attached  to  the  ridge  passing  upwards  from  the 
■external  condyle  of  the  humerus,  inferiorly  it  blends  with 
•caput  medium. 

Extensor  metacarpi  magnus  at  its  superior  attachment 
to  the  ridge  running  upwards  from  the  external  condyle  of 
the  humerus,  blends  with  extensor  pedis.  It  is  also  at- 
tached by  a  strong  tendon  to  the  anterior  part  of  the  cap- 
sular ligament  of  the  elbow- joint,  thus  separating  humerali* 
•externus  from  that  ligament.  Between  the  upper  part  of 
this  muscle  and  humeralis  externus  runs  the  spiral  nerve, 
which  after  meeting  the  spiral  artery  and  vein  and  their 
small  accompanying  nerve  at  the  front  of  the  joint  proceeds 
with  them  down  the  front  of  the  limb  under  the  muscles. 
At  the  upper  part  of  the  front  of  the  knee  its  tendon  is  in 
contact  with  extensor  metacarpi  obliquus,  which  passes  over 
it  in  its  course  from  without  inwards  and  downwards,  and 
is  separated  from  it  by  a  bursa.  Passing  then  through  the 
central  one  of  the  three  grooves  at  the  anterior  part  of  the 
inferior  extremity  of  the  radius,  and  through  a  special 
channel  in  the  annular  ligament  of  the  knee,  where  it  is 
lubricated  with  synovia,  the  tendon  of  this  muscle  becomes 
inserted  into  the  j)rominence  on  the  antero-superior  part  of 
the  large  metacarpal  bone,  slightly  inclined  to  the  inner  side. 


212  OUTLINES    or    EQUINE    ANATOMY. 

Extensor  metacarpi  obliqiuis  arises  from  the  outer  part 
of  tlie  middle  third  of  the  radius  "between  extensor' 
suffraginis  and  extensor  j)edis.  Its  muscular  fibres  in 
running  under  the  tendon  of  extensor  pedis  converge,  and 
they  form  a  tendon  which  runs  over  extensor  metacarpi 
magnus  (from  wdiich  it  is  separated  by  a  bursa),  passes 
through  the  oblique  groove  on  the  inner  surface  of  the  in- 
ferior extremity  of  the  radius,  through  a  channel  in  the 
annular  ligament  of  the  knee,  lubricated  by  synovia,  ta 
become  inserted  into  the  head  of  the  inner  small  meta- 
carpal bone  through  the  medium  of  the  inner  lateral 
ligament  of  the  knee. 

Extensor  pedis  has  a  penniform  arrangement.  Supe- 
riorly it  blends  with  extensor  metacarjn  magnus  in  becoming' 
attached  to  the  external  condyle  of  the  humerus,  and  its- 
fibres  are  attached  to  the  inner  lateral  and  capsular  liga- 
ments of  the  elbow-joint,  and  to  the  outer  part  of  the 
radius  as  far  down  as  the  inferior  part  of  the  superior 
third.  A  remarkable  round  band  of  its  muscular  fibres 
runs  underneath  extensor  suffraginis  to  the  foramen 
between  the  ulna  and  the  radius,  where  it  becomes 
attached  in  contact  with  the  branches  of  the  radial  vessels 
which  pass  through  the  foramen.  While  passing  over  ex- 
tensor metacarpi  obliquus  the  muscle  becomes  tendinous 
and  passes  through  the  antero-external  groove  at  the 
antero- inferior  part  of  the  radius  and  the  annular  ligament 
in  a  special  channel,  lubricated  with  synovia.  Beloio  the 
Tcnee  it  sends  a  hranch  to  assist  in  foroning  Ugamenium  ex-- 
tensorum.  Between  the  upper  part  of  this  muscle  and 
extensor  metacarpi  magnus  is  a  slight  inflection  of  the 
faschia  of  the  arm,  but  a  much  thicker  fold  separates  it  from 

Extensor  suiFraginis,  and  forms  a  sheath  in  which 
this  muscle  plays,  and  whereby  from  the  elbow  to  the  knee 
it  is  firmly  fixed  to  the  lateral  part  of  the  radius.  It- 
arises  superiorly  through  the  medium  of  the  external' 
lateral  ligament  from  the  outer  condyle  of  the  humerus, 
at  first  forms  a  bridge  over  the  erratic  portion  of  extensor 
pedis  and  then  becomes  fixed  to  the  radius  as  above 
mentioned.  It  passes  through  the  external  groove  on 
the  antero-inferior  part  of  the  radius,  and  through  the 
annular  ligament,  from  which  it  receives  a  fibrous  cord 
opposite  the  head  of  the  small  metacarpal  bone,  and 
below  the  knee  becomes  rather  expanded  on  the  external' 


THE    FORE    EXTREMITY.  213 

■surface  of  tlie  large  metacarpal  boue,  receives  a  portion  of 
tendon  from  extensor  pedis,  and  is  liere  termed  liga- 
jnentuni  extensorum.  After  passing  over  tlie  capsular 
ligament  of  the  fetlock -joint  to  which  it  is  attached,  it 
becomes  inserted  into  the  supero-anterior  and  external  part 
of  OS  suffraginis. 

Flexor  metacarpi  externus,  superiorly,  is  attached  to  the 
-extreme  posterior  part  of  the  ridge  running  from  the  ex- 
ternal condyle  of  the  humerus  and  to  the  capsular  ligament 
of  the  elbow-joint  (being  the  only  flexor  of  the  forearm 
which  arises  from  the  outer  surface  of  the  limb)  ;  it  runs 
downwards  and  inferiorly  blends  with  the  fibrous  sheath 
of  extensor  os  suffraginis  (which  is  here  part  of  the 
annular  ligament  of  the  knee),  becoming  inserted  into  the 
superior  margin  of  the  trapezium,  while  it  sends  a  small 
round  tendon  through  the  groove  running  obliquely  down- 
wards and  forwards  on  the  external  surface  of  this  bone 
^which  is  lubricated  with  synovia),  and  passes  to  the  head 
of  the  outer  splint  bone. 

Remove  the  skin  from  the  remainder  of  the  limb  as 
far  as  the  hoof,  clean  the  tendons  and  ligaments  thus  ex- 
posed by  careful  removal  of  the  areolar  tissue  anteriorly ; 
the  tendon  of  extensor  os  suffraginis  will  be  found  arranged 
as  above  indicated ;  that  of  extensor  pedis,  after  playing 
over  a  large  bursa  at  the  antero-inferior  part  of  the  large 
metacarpal  bone,  grows  wider  in  becoming  attached  to  the 
front  of  the  capsular  ligament  of  the  fetlock,  receives  on 
each  side  a  strong  band  running  from  the  inferior  extremity 
of  the  superior  sesamoideal  ligament  obliquely  over  the 
lateral  parts  of  the  pastern  bone,  and  becomes  inserted  into 
a  somewhat  heart-shaped  prominence  on  the  anterior  sur- 
face of  the  coronal  process  of  os  pedis.  It  is  firmly  fixed 
to  the  anterior  surfaces  of  ossa  coronse  and  suffraginis,  and 
of  the  capsular  ligaments  of  the  pastern  and  cofiin  joints 
by  dense  white  fibrous  tissue,  and  in  the  same  way  is  united 
on  both  sides  of  its  extreme  inferior  part  to  the  lateral 
.cartilages. 

From  the  inferior  margin  of  trapezium  a  portion  of  the 
annular  ligament  runs  to  the  supero-lateral  part  of  the 
•small  external  metacarpal  bone ;  it  serves  to  protect  the 
jierves  and  blood-vessels  of  this  neighbourhood. 

The  radial  artery  breaks  up  into  two  vessels  just  at  the 
.superior  suspensory  ligament,  the  smaller,  small  metacarpal 


214  OUTLINES   OF   EQUINE   ANATOMY. 

artery,  passes  over  the  annular  ligament  of  the  knee  and 
subsequently  becomes  internally  placed  to  the  inner  splint 
bone.  At  about  the  inferior  part  of  the  superior  third  of 
the  posterior  surface  of  the  large  metacarpal  bone  it  gives 
off  the  medullary  artery  of  that  hone,  and  about  at  the  bifur- 
cation of  the  superior  sesamoideal  ligament  it  anastomoses 
vfith  a  small  recurrent  hranch  of  the  large  metacarpal 
artery,  which  we  last  noticed  as  being  enclosed  with  the 
nerves  in  the  synovial  sheath  of  the  flexor  tendons  at  the 
back  of  the  knee.  It  (the  large  metacarpal)  passes  doAvn 
the  back  of  the  leg  in  contact  with  the  inner  margin  of 
these  tendons,  and  subsequently  between  them  and  the  su- 
perior sesamoideal  ligament,  where  it  gives  off  the  recurrent 
branch,  and  then  bifurcates  to  form  the  plantar  arteries. 
If  we  trace  out  one  of  these  arteries  we  shall  find  that  it 
passes  on  to  the  lateral  part  of  the  fetlock,  where  it  is  sub- 
cutaneous and  where  the  corresponding  vein  is  in  front,  the 
nerve  behind  it.  It  gives  off  a  large  branch  forwards,  ramify- 
ing in  front  of  os  suffraginis,  and  small  unnamed  branches 
hacJctvards  to  the  heel,  and  then  runs  directly  to  the  internal 
surface  of  the  lateral  cartilage.  Just  at  the  lateral  part  of  the 
cofiin- joint  it  gives  two  branches  forwards  and  one  back- 
wards. The  two  running  forwards  anastomose  with  their  fel- 
lows from  the  opposite  side  at  the  front  of  the  coronet,  one 
externally  situated  to  the  extensor  pedis  tendon  being  the 
superficial  coronoj^'y  and  sending  on  either  side  of  the 
tendon  a  branch  inwards  to  the  other,  which  being  inter- 
nally placed  to  the  tendon  is  termed  the  deep-seated  coro- 
nary artery.  The  posterior  hranch  goes  to  the  frog  and 
bifurcates,  one  of  its  branches  running  to  the  bulb,  one  to 
the  apex  of  that  organ,  each  of  them  anastomoses  with  its 
fellow.  The  plantars  give  off  the  lateral  laminal  arteries, 
while  running  over  the  internal  surface  of  the  lateral  car- 
tilages, and  these  pass  outwards  through  the  foramen  in 
the  wing  of  the  os  pedis  (or  between  os  jDedis  and  the 
cartilage),  running  forwards  in  a  groove  to  anastomose  at 
the  front  of  the  bone  with  each  other,  and  giving  branches 
superiorly  to  the  coronary  arteries,  inferiorly  to  the  circum- 
flex artery  of  the  toe,  and  inwards  to  the  arterial  circle 
formed  in  the  substance  of  os  pedis  by  the  anastomosis  of 
the  two  plantars,  which,  after  jmssing  through  grooves  on 
the  under  surface  of  os  pedis  between  the  inferior  broad 
ligament  of  the  navicular  bone  and  the  perforans  tendon, 


THE    FORE   EXTREMITY.  215 

enter  the  bone  througli  the  foramina  on  its  plantar 
surface.  Branches  running  downwards  through  the  sub- 
stance of  the  bone  from  this  circulus  arteriosus  of  the 
foot  pass  out  of  the  large  foramina  at  the  outer  margin  of 
the  plantar  surface  of  os  pedis,  where  they  form  a  continu- 
ous arterial  circle,  the  circumflex  artery  of  the  toe,  which 
receives  branches  superiorly  from  the  lateral  laminal  arte- 
ries, which  sometimes  mainly  form  it ;  and  on  the  plantar 
surface  some  large  arteries  (solar)  radiate  to  it  from  the 
artery  of  the  apex  of  the  frog.  It  will  be  thus  seen  that 
the  arteries  form  an  intricate  plexus,  not  only  in  the  sensi- 
tive structures,  but  also  in  the  bones  of  the  foot ;  the  veins 
are  more  numerous,  they  form  an  intraosseous  plexus,  the 
vessels  of  which  mainly  converge  to  a  trunk  corresponding 
to  the  plantar  arteiy  inside  the  lateral  cartilage  ;  and  also  a 
superficial  plexus  composed  of  vessels  with  but  small  meshes, 
which  are  found  in  the  whole  of  the  vascular  investing  and 
secreting  layer  of  the  foot,  they  converge  towards  certain 
larger  veins  which  are  on  the  external  surface  of  the  lateral 
cartilages  and  form  a  vein  which  unites  above  the  cartilage 
with  the  intraosseous  vein  to  form  the  plantar  which  runs 
upwards  (receiving  branches), with  and  in  front  of  the  artery 
to  unite  with  its  fellow  above  the  fetlock.  From  this  junction 
four  or  five  vessels  inin  upwards,  bemg  the  satellites  of  the 
large  and  small  metacarpal  arteries,  and  form  the  radial  and 
superficial  brachial  veins  respectively;  since  the  smaller  veins 
of  the  foot  have  no  valves,  they  can  be  injected  from  the 
plantar. 

After  passing  with  the  flexor  tendons  through  the  annu- 
lar ligament  of  the  knee,  the  metacarpal  nei*ves  accompany 
the  tendons  as  far  as  opposite  the  superior  part  of  the 
inferior  third  of  the  large  metacarpal  bone.  The  external 
metacarpal  nerve  is  derived  from  the  ulnar,  the  internal 
metacarpal  nerve  from  the  radial.  The  internal  gives  olf 
fibres  which  form  a  trunk  extending  obliquely  downwards 
and  outwards  between  the  skin  and  the  flexor  tendons  to 
the  external  metacarpal  nerve.  At  the  side  of  the  fetlock 
each  nerve  divides  into  three  parts  ;  one  runs  over  the  front 
of  OS  suffraginis  ;  it  is  separated  by  the  plantar  vein  from 
the  middle  branch  which  runs  to  the  coronet,  and  is 
separated  by  the  plantar  artery  from  the  posterior  plantar 
nerve  which  supplies  the  major  portion  of  the  foot  witfe 
nerve  force. 


:216  OUTLINES    OF   EQUINE   ANATOJIY. 


PART  VIII.— SPECIAL  ANATOMY. 

The  Abdomen. 

The  operator  commences  by  dissecting  tbe  skin  down- 
wards from  tlie  middle  tlioracic  incision  towards  the  middle 
line  of  tbe  abdomen.  Thus  he  exposes  the  panniculus,  ex- 
tending over  the  lateral  part  of  the  belly  from  the  external 
surface  of  the  shoulder.  Infero-anteriorly  is  situated  ])ec- 
toralis  magnus,  which  is  superiorly  slightly  covered  by 
panniculus  ;  it  is  about  five  inches  wide,  and  covers  about 
one  third  of  the  length  of  the  under  surface  of  the  belly. 
Posteriorly  the  panniculus  divides  into  two  layers,  one  of 
which  covers  the  outer  surface  of  the  quarter,  the  other 
runs  to  the  inner  surface  and,  as  these  two  layers  are  in- 
timately connected,  a  somewhat  tense  sheath  is  formed, 
which  is  superiorly  attached  to  the  antero -inferior  spinous 
process  of  the  ilium,  inferiorly  around  the  patella.  It  blends 
posteriorly  with  the  faschia  of  the  quarter.  It  is  the  por- 
tion of  panniculus  extending  to  this  sheath  in  the  ox,  which, 
covered  by  skin,  foiins  that  thin  fold  termed  by  butchers 
"  the  flank."  Below  this  is  the  superficial  abdominal 
faschia,  a  smooth  yellow  layer  formed  of  elastic  tissue  which 
is  immediately  subcutaneous.  It  is  widely  spread  over  the 
aponeurotic  expansions  of  the  abdominal  muscles  as  far 
forwards  as  the  ensiform  cartilage,  backwards  as  the  sym- 
physis pubis.  Thick  towards  the  linea  alba,  gradually 
grows  thinner  on  approaching  the  muscular  portion  of 
obliquus  abdominis  externus,  and  at  the  postero-inferior 
part  sends  a  process  which,  in  the  male,  combines  with  that 
-of  the  opposite  side,  forming  the  suspensory  ligament  of  the 
^eniSfi-a.  thefemale  the  elastic  divestment  which  covers  themam- 
mary  gland,  and  which  sends  trabeculae  inwards  to  separate 
its  lobes.  Internally  this  layer  is  attached  to  the  external 
oblique  abdominal  muscle,  externally  it  affords  attachment 
to  pectoralis  magnus  anteriorly,  posteriorly  it  becomes 
inflected  to  the  internal  surface  of  the  thigh* 


THE    ABDOMEN.  ^17 

Tlie  fore  limb  should  now  he  elevated  by  means  of  an 
iron  fork,  and  tlie  pectoral  muscles  dissected.  Pectoralis 
transversus  is  superficially  situated,  it  blends  witli  its 
fellow  at  tlie  under  part  of  the  cariniform  cartilage,  and 
anterior  part  of  the  sternum,  being  connected  to  these  firmly 
•at  its  anterior  part  by  areolar  tissue  ;  x^osteriorly,  as  far 
as  the  lower  extremity  of  the  fifth  rib,  so  that  it  has 
free  play  over  this  surface  ;  from  this  its  fibres  run  to 
the  inner  side  of  the  fore  limb,  and  with  levator  humeri 
become  attached  to  the  fibrous  band  running  from  the 
inferior  extremities  of  the  humeral  ridge  to  the  infero-ex- 
ternal  part  of  the  humerus. 

Anteriorly  to  the  firm  attachment  of  pectoralis  trans- 
versus is  the  originating  point  of  sterno-maxillaris,  above 
which  sterno-thyrO'hyoideus  is  attached  to  the  cariniform 
cartilage.  Higher  up  pectoralis  anticus  is  attached  to  the 
lateral  part  of  the  sternum,  extending  as  far  back  as  about 
the  fourth  sternal  bone,  and  being  slightly  united  to  the 
corresponding  sterno-costal  cartilages ;  it  runs  upwards 
to  the  antero-superior  part  of  the  scapula. 

Pectoralis  mag^nus  runs  from  the  post ero -lateral  part  of 
the  sternum,  and  from  the  under  surface  of  the  ensiform 
cartilage  and  from  the  anterior  part  of  faschia  superficialis 
abdominis  to  the  external  and  internal  tubercles  upon  the 
anterior  part  of  the  head  of  the  humerus,  where  it  is  at- 
tached with  antea  spinatus,  and  between  which  attachments 
runs  the  superior  cartilaginous  tendon  of  flexor  bracliii. 

By  section  of  the  pectoral  muscles  a  quantity  of  loose 
areolar  tissue  is  shown,  into  the  inferior  part  of  which 
subscapulo-hyoideus  seems  to  be  attached,  gaining  ap- 
parently a  very  unsubstantial  origin.  The  axillary  artery 
may  now  be  seen  running  to  the  internal  surface  of  the 
shoulder- joint,  while  the  axillary  plexus  of  nerves  is  seen 
sending  off  numerous  trunks.  The  axillary  artery  after 
being  given  off  by  the  arteria  innominata,  winds  round  a 
smooth  surface  on  the  anterior  border  of  the  first  rib  below 
the  inferior  attachment  of  the  scalenus  muscle ;  on  gain- 
ing the  internal  surface  of  the  shoulder- joint  it  breaks  up, 
sending  the  humeral  thoracic  branch  anteriorly  to  pector- 
alis magnus  and  antea  spinatus  at  their  insertion  ;  the 
anterior  scapular  between  subscapularis  and  antea  spina- 
tus to  the  anterior  dorsal  fossa  of  the  scapula ;  the  pos- 
terior scapular  or  subscapular  artery,  which  passes  under 


218  OUTLINES   OF   EQUINE   ANATOMY. 

teres  internus,  and  runs  between  this  muscle  and  tlie  caput 
magnum  of  triceps  extensor  brachii,  to  the  posterior  angle 
of  the  scapula ;  and  the  external  thoracic  artery,  which 
runs  backwards  to  the  lateral  j^art  of  the  thorax,  under 
latissimus  dorsi.  Inferiorly  the  humeral  artery  runs  from 
the  axillary  artery  towards  the  elbow-joint,  sending  off 
several  constant  branches,  and  finally  breaking  up  into  the 
tdnar,  spiral,  and  radial  branches  :  the  ulnar  runs  to  break 
up  about  the  point  of  the  ulna,  sending  an  important 
branch  down  the  limb  beneath  ulnaris  accessorius ;  the 
spiral  twists  round  the  front  of  the  humerus ;  the  radial 
runs  along  the  internal  surface  of  the  limb. 

I  have  thus  particularised  these  arteries,  since  with  each 
of  these  runs  a  nerve  from  the  axillary  plexus,  which, 
being  formed  by  branches  from  the  sixth,  seventh,  and 
eighth  cervical  nerves,  and  the  first  dorsal  (with  a  sym- 
pathetic branch),  passes  between  the  long  and  short  heads 
of  scalenus,  and  breaks  up  into  the  humeral  thoracic,  ex- 
ternal thoracic,  anterior  and  ^posterior  scajoular,  tdnar,  spiral^ 
and  radial  nerves. 

By  division  of  the  pectorals  we  have  exposed  the  lateralis 
sterni,  running  in  a  downward  and  backward  direction 
from  the  posterior  border  of  the  lower  third  of  the  first 
rib,  to  be  attached  below  the  inferior  extremity  of  the  fourth 
sterno-costal  cartilage  to  the  lateral  part  of  the  sternum. 
This  muscle  being  removed,  we  have  the  intercostales 
interni  as  continued  between  the  sterno-costal  cartilages 
exposed  to  view;  they  run  in  a  downward  and  forward 
direction,  obliquely  from  the  anterior  border  of  one  carti- 
lage to  the  posterior  border  of  the  one  immediately  in 
front  of  it.  Posteriorly  they  are  covered  by  the  anterior 
extremity  of  rectus  abdominis,  which  is  anteriorly  attached 
to  the  external  surface  of  the  three  or  four  posterior  sternal 
cartilages  of  the  true  ribs. 

Having  examined  these  structures,  we  remove  the 
aponeurotic  layer  covering  serratus  magnus,  and  thus 
expose  its  inferior  attachments.  It  will  be  found  to  arise 
from  the  transverse  processes  of  the  five  posterior  cervical 
vertebrae,  and  from  the  external  surface  of  the  eight  true 
ribs,  having  four  digitations  posteriorly  with  obliquus 
abdominis  externus ;  from  these  points  its  fibres,  forming 
a  large  fleshy  slab  of  muscle,  converge  towards  the  superior 
margin  of  the  venter  surface  of  the  scapula,  into  which  they 


THE   ABDOMEN.  219 

become  inserted  between  the  attachments  of  rbomboideus. 
and  subscapularis,  some  of  the  fibres  running  to  the  ex- 
ternal surface  of  the  cartilage  of  elongation  at  its  posterior 
part.  This,  with  the  corresponding  muscle  of  the  opposite 
side,  forms  a  slingby  which  the  body  is  anteriorly  supported. 

The  following  are  the  muscles  by  which  the  fore  extremity 
is  connected  to  the  trunk : — panniculus  carnosus,  levator 
humeri,  rhomboideus,  trapezius,  latissimus  dorsi,  pectorales 
magnus,  anticus,  and  transversus,  subscapulo-hyoideus,  and 
serratus  magnus. 

The  f  aschia  superficialis  abdominis  must  be  now  removed 
with  care,  for  on  the  proper  removal  of  this  depends  the 
successful  demonstration  of  the  aponeuroses  of  the  abdo- 
minal muscles.  If  it  has  become  too  dry  for  removal,  it  is 
better  to  raise  it  with  the  tendon  of  obliquus  abdominis 
externus,  the  fibres  of  which  run  downwards  and  backwards 
towards  the  linea  alba.  This  is  a  thick  elastic  band,  formed 
by  the  general  union  of  the  abdominal  muscles  at  the 
middle  line  of  the  abdomen,  extending  from  the  ensiform 
cartilage  to  the  symphysis  pubis,  before  arriving  at  which 
it  becomes  broader  and  receives  fibres  from  the  several 
tendons  of  the  abdominal  muscles,  and  a  distinct  band 
of  tendinous  fibres  from  the  antero-inferior  spinous  pro- 
cess of  the  ilium,  Poupart's  ligament  or  the  crural  arch. 
Into  this  ligament  (which  is  really  but  a  portion  of  obli- 
quus abdominis  externus),  the  posterior  fibres  of  the 
external  oblique  are  inserted,  and  between  these  and  those 
inserted  into  the  linea  alba  is  the  external  abdominal  ring", 
through  which  passes  the  spermatic  cord,  covered  by  the 
cremaster  muscle.  It  runs  upwards  from  the  external  ring 
posteriorly  towards  the  antero-inferior  spinous  process  of 
the  ilium,  the  cremaster  becoming  lost  in  the  lumbar 
faschia ;  the  remainder  of  the  cord  resting  on  obliquus 
abdominis  internus,  at  length  passes  between  its  fibres 
and  gains  the  abdominal  cavity  at  the  internal  abdo- 
minal ring,  the  space  between  the  two  rings  being  the 
inguinal  canal.  This  is  the  passage  between  the  external 
oblique  and  the  internal  oblique  muscles ;  it  terminates^ 
superiorly  at  the  internal  abdominal  ring,  which  is  formed 
by  the  passage  of  the  prolongation  of  the  peritoneum  from 
the  floor  of  the  abdomen  to  line  the  scrotum,  forming  the 
tunica  vaginalis  scroti;  this  passes  between  fibres  of  the 
internal  oblique  muscle.     Situated  at  about  the  anterion 


220  OUTLINES   OF   EQUINE   ANATOMY. 

part  of  tlie  posterior  third  of  tlie  linea  alba  is  the  umbi- 
licus ;  this  is  a  slight  puckering  of  the  layers  forming  the 
iloor  of  the  abdomen  to  close  ujd  an  opening  which,  in  the 
foetus,  admitted  the  passage  of  the  umbilical  arteries  and 
the  urachus  to  the  foetal  membranes,  and  the  umbilical 
veins  from  them  ;  it  becomes  impervious  in  extra-uterine  life, 
being  no  longer  needed. 

Obliquus  abdominis  externus  is  attached  to  the  external 
surface  of  the  fourteen  posterior  ribs  almost  as  low  down 
as  their  cartilages,  having  anteriorly  four  fleshy  digitations 
with  serratus  magnus.  From  these  points  its  fibres  run 
•obliquely  downwards  and  backwards  to  the  under  surface 
of  the  ensiform  cartilage,  the  linea  alba,  symphysis  pubis, 
antero-inferior  spinous  process  of  the  ilium  and  lumbar 
faschia.  Some  of  the  fibres  are  arranged  to  form  Poupart's 
ligament  (vide  supra)  into  which  others  are  inserted,  while 
some  run  to  become  attached  by  aponeurosis  to  the  internal 
.  surface  of  the  hind  limb.  Removing  this  muscle  we  expose 
some  thin  tendinous  fibres  running  obliquely  downwards 
and  forwards ;    these  belong  to 

Obliquus  abdominis  internus,  which  seems  to  be  composed 
of  fibres  radiating  from  the  antero-inferior  spinous  process 
of  the  ilium  and  the  lumbar  faschia  and  the  transverse 
processes  of  the  three  anterior  lumbar  vertebrae.  The  most 
superior  of  these  run  to  the  last  rib,  and  being  slightly 
separated  from  the  rest  are  sometimes  considered  as  a  dis- 
tinct muscle  and  termed  retractor  costae  ;  a  few  run  to  the 
internal  surface  of  the  posterior  cartilages  of  the  false  ribs, 
most  of  them  running  to  the  linea  alba  along  its  whole 
length,  the  posterior  ones  separating  to  form  the  internal 
abdominal  ring  and  the  inner  wall  of  the  inguinal  canal. 

Extending  for  a  considerable  distance  on  either  side  of 
the  linea  alba,  forming  the  under  part  of  the  wall  of  the 
belly,  we  see  a  muscle  wide  centrally  and  growing  narrow 
■anteriorly  to  become  attached  to  the  under  surface  of  the 
■  ensiform  cartilage  and  to  the  external  surface  of  the  four 
posterior  sterno-costal  cartilages  of  the  true  ribs.  Poste- 
riorly it  grows  narrow  to  become  attached  to  the  thick  tendon 
running  to  the  anterior  part  of  symphysis  pubis  ;  its  inner 
margin  is  attached  along  the  whole  length  of  linea  alba, 
and  it  presents  many  transverse  tendinous  markings, 
by  which  it  is  considerably  strengthened  ;  this  is  rectus 
.abdominis,  its  internal  surface  lies  in  contact  with  a  few 


THE  ABDOMEN.  221 

scattered  tendinous  fibres  apparently  belonging  to  the 
internal  oblique  muscle.  Having  removed  these  we  see'^ 
trausversalis  abdominis,  on  the  external  surface  of  which 
certain  nerves  rendered  consinciious  by  their  tvhiteness  run- 
directly  from  the  intervertebral  lumhar  and  posterior  doi^sal 
nerves,  in  a  direction  similar  to  the  fibres  of  this  muscle, 
which  run  perpendicularly  to  the  linea  alba.  On  the  ex- 
ternal surface  of  this  muscle  we  also  see  the  arteries  which 
supply  the  abdominal  walls  with  blood  and  their  accom- 
panying veins.  Superiorly  lumbar  branches,  derived  directly 
from  the  posterior  aorta,  and  the  circumflex  artery  of  the 
ilium,  which  arises  from  the  external  iliac  artery,  runs 
directly  to  the  antero-iuferior  spinous  process,  and  then, 
breaks  up  in  supplying  the  abdominal  muscles.  Posteriorly 
the  epigastric  is  given  off  by  arteria  profunda  femoris 
below  symphysis  pubis,  and  passing  over  the  internal  sur- 
face of  the  femoral  artery  and  of  the  inguinal  canal,  runs- 
forwards  under  rectus  abdominis  ;  it  sends  off  the  external 
fudic  artery  to  the  sheath  in  the  male,  the  mammary 
gland  in  the  female ;  in  the  male  also  the  external  pudic 
artery  gives  off  the  anterior  dorsal  artery  of  the  ;penis,  one 
branch  of  which  runs  forwards  along  the  superior  part  of 
the  organ  as  far  as  the  glans,  the  other  backwards  to  anas- 
tomose with  the  posterior  dorsal  artery  from  the  internal 
pudic. 

The  internal  thoracic  artery  at  the  ensiform  cartilage 
divides,  sending  one  branch,  the  anterior  abdominal,  along 
the  floor  of  the  abdomen,  the  other  upwards  along  the  infe- 
rior extremities  of  the  ribs,  where  it  anastomoses  with  the 
intercostals,  and  sends  twigs  to  the  abdominal  walls : 
all  these  arteries  anastomose  by  their  terminal  twigs  one 
with  the  other. 

Transversalis  abdominis  arises  from  the  internal  sur- 
face of  the  twelve  posterior  ribs,  of  their  cartilages,  and 
by  faschial  expansion  from  the  transverse  processes  of  the 
lumbar  vertebrae,  its  fibres  run  to  be  inserted  perpendicu- 
larly into  the  upper  surface  of  the  ensiform  cartilage  and 
the  linea  alba.  Anteriorly  inside  the  ribs  its  attachments 
digitate  with  those  of  the  diaphragm.  Posteriorly  its 
fibres  grow  gradually  more  and  more  sparse,  none  being 
found  at  the  internal  abdominal  ring.  By  removing  this 
muscle  we  expose  the  peritoneum  or  serous  lining  mem- 
brane of  the  abdomen  covered  in  places  by  white  fibres 


222  OUTLINES   OF   EQUINE   ANATOMY. 

Avhicli  serve  to  strengthen  it.  It  is  transparent  and 
through  it  we  see  the  caecum  and  colon,  with  their  longitu- 
dinal muscular  bands  and  resulting  puckerings. 

The  abdominal  cavity  is  bounded  anteriorly  by  the 
diaphragm,  inferiorly  and  laterally  by  the  abdominal 
muscles,  superiorly  by  the  ]3S08e  muscles  attached  under- 
neath the  lumbar  vertebrae,  posteriorly  by  the  pelvis  with 
its  viscera.  Its  anterior  surface  is  concave,  in  consequence 
of  the  concavity  of  the  diaphragm  against  which  the  liver 
rests  on  the  right  side,  the  stomach  and  the  spleen  mainly 
on  the  left. 

On  laying  open  the  cavity  from  below  at  the  linea 
alba  we  expose  the  various  viscera  all  covered  by  peri- 
toneum, so  that  none  of  them  can  be  touched  except 
after  removal  of  their  investing  serous  layer :  it  likewise 
forms  several  double  reflections  around  the  viscera,  which 
serve  to  support  the  organs  and  which  receive  special 
names.  After  covering  the  floor  and  the  sides  of  the 
belly  it  runs  upwards  posteriorly  to  be  reflected  to  form 
the  ligaments  of  the  bladder ;  from  the  floor  of  the  belly 
along  the  central  line  a  double  fold  runs  to  the  fundus  or 
anterior  portion  of  the  bladder,  being  the  susj^ensory  liga- 
ment. From  the  sides  hroad  ligaments  run  horizontally 
to  the  fundus,  and  on  the  free  margin  of  each  between 
the  folds  of  peritoneum,  is  situated  the  round  ligament 
of  the  bladder,  which  in  the  foetus  is  the  umbilical  artery  ; 
it  arises  from  the  artery  of  the  bulb,  and  in  the  adult 
becomes  impervious.  The  broad  ligaments  separate  to 
enclose  the  bladder,  and  the  layer  forming  the  ui)per  surface 
of  these  ligaments  and  covering  the  upper  surface  of  the 
bladder  is  posteriorly  inflected  upwards  on  to  the  under 
surface  of  the  commencement  portion  of  the  rectum  and 
the  single  colon,  on  either  side  of  which  the  membrane 
becomes  firmly  attached,  superiorly  forming  by  the  union 
of  the  two  layers  the  meso-rectum,  by  which  this  portion 
of  the  intestine  is  supported  against  the  spine,  and  which 
extends  almost  as  far  forwards  as  the  stomach.  On  ar- 
riving at  the  lumbar  region  it  gives  off  a  pouch  on  the 
right  side  in  which  are  enclosed  the  double  colon  and  the 
caecum  and  which  forms  the  meso-colon,  and  the  meso- 
caecum,  and  another  on  the  left  in  which  the  small  intes- 
tines lie,  which  is  termed  the  mesentery ;  from  this  pos- 
teriorly a  smaller  fold  extends  on  the  right  side  around 


THE   ABDOMEN.  223 

tlie  duodenum  whicli  it  connects  to  tlie  porta  of  the  liver, 
and  from  the  anterior  extremity  of  the  bowel  is  continued 
one  layer  over  the  ant ero -inferior  surface  of  the  stomach. 
After  tracing  the  peritoneum  thus  far  from  behind  we 
may  commence  to  examine  it  anteriorly.  Passing  forwards 
from  the  umbilicus  on  the  floor  of  the  abdomen  it  forms 
centrally  a  longitudinal  fold  which  runs  from  behind 
forwards,  extending  farther  back  in  young  subjects  than 
in  old ;  this  is  one  of  the  ligaments  of  the  liver,  falciform 
or  suspensory  ligament.  It  runs  on  to  the  posterior  surface 
of  the  diaphragm  and  extends  as  far  as  foramen  dextrum  ; 
on  its  free  margin,  enclosed  between  the  two  layers,  is  an  im- 
pervious fibrous  cord,  round  ligament,  which  is  the  dege- 
nerated umbilical  vein  of  the  foetus  by  which  the  blood  is 
carried  from  the  umbilicus  to  the  liver.  It  is  this  liga- 
ment which  is  sometimes  inquired  after  as  being  "  the 
only  ligament  of  the  liver  not  formed  by  peritoneum." 
The  layers  of  serous  membrane  forming  the  falciform 
ligament  separate  superiorly  and  in  surrounding  the  j)os- 
terior  vena  cava  in  its  course  from  the  liver  to  the  foramen 
dextrum  form  the  coronary  ligament.  The  peritoneum 
then  forms  the  right  lateral  ligament,  running  from  the 
superior  margin  of  the  right  lobe  of  the  liver ;  this  liga- 
ment is  broad  and  wide,  and  on  its  posterior  surface  we 
may  see  a  small  special  ligament  passing  to  the  lohuhis 
Spigelii;  its  posterior  layer  is  reflected  from  the  roof  of 
the  abdominal  cavity  at  the  right  kidney.  A  correspond- 
ing ligament,  but  longer  and  narrower,  runs  from  the  pos- 
terior surface  of  the  left  side  of  the  diaphragm  to  the  left 
extremity  of  the  superior  margin  of  the  liver,  which  is  the 
left  lateral  ligament.  After  investing  the  liver  the  serous 
membrane  forms  the  gastric  liejmtic  omentum  which  runs 
from  the  transverse  fissure  of  the  liver  to  the  lesser  cur- 
vature of  the  stomach  and  to  the  attachment  of  the  duo- 
denum to  the  spine  ;  between  its  layers  run  the  hepatic  and 
pancreatic  ducts.  The  stomach  will  be  found  to  be  enclosed 
in  a  sac,  which,  in  consequence  of  the  fatty  matter  between 
its  layers  arranged  around  its  vessels,  is  apparently  reti- 
culated. This  is  the  omentum  major  or  gastro-colic  omentum 
{caul),  which  forms  a  peculiar  cavity  connected  with  the 
general  peritoneal  cavity  by  a  channel,  foramen  of  Winslow, 
which  is  situated  below  the  spine  against  the  coeliac  axis. 
The  reflections  of   peritoneum  from  the  stomach  to  the 


224  OUTLINES    OF    EQUINE    ANATOMY. 

neighbouring  viscera  are  termed  omenta  :  we  have  noticed 
the  gastro-hepatic,  and  gastro- colic  omenta ;  from  the  left 
extremity  of  the  greater  curvature  the  (jastro-spleniG 
omentum  passes  to  the  spleen,  which  is  suspended  between 
its  two  folds  ;  and  to  the  extreme  left  part  of  the  greater' 
curvature  the  cjastric-plirenic  omentum  is  reflected  from  the 
diaphragm,  it  terminates  in  forming  the  cardiac  ligament 
surrounding  the  terminating  portion  of  the  oesophagus. 

In  the  male  at  the  internal  abdominal  rings  on  either 
side  at  the  posterior  part  of  the  cavity  the  peritoneum  is 
reflected  through  the  inguinal  canal  into  the  scrotum, 
forming  tunica  vaginalis  scroti,  which  by  a  serous  frsenum 
is  connected  with  tunica  vaginalis  testis,  a  reflection  from 
the  roof  of  the  cavity.  There  is  also  a  slight  fold  connecting^ 
the  tvjo  terminal  portions  of  the  vasa  defer  entia  together,  between 
tuhich  lies  the  third  vesicula  seminalis.  In  the  female  from 
the  u]3per  surface  of  the  bladder  it  passes  to  the  anterior 
portion  of  the  vagina  and  invests  the  uterus,  from  the 
horns  of  which  it  passes  to  the  roof  of  the  cavity,  forming- 
the  hroad  ligaments,  which  anteriorly  contain  the  ovaries 
and  fallopian  tubes,  and  which  have  the  round  ligaments  of 
the  uterus  and  those  of  the  ovary  between  their  double  layers. 
Between  the  two  horns  the  serous  membrane  is  reflected 
backwards  over  the  upper  surface  of  the  body  of  the  uterus 
to  the  vagina,  from  which  it  passes  upwards  to  the  under 
surface  of  the  anterior  part  of  the  rectum. 

By  incision  through  the  terminal  portion  of  the  oesophagus, 
through  the  rectum,  and  through  their  serous  connections 
to  the  neighbouring  organs,  especially  up  against  the  spine, 
the  intestines  and  stomach  may  be  removed  from  the  abdom- 
inal cavity.  In  the  process  we  expose  the  pancreas,  a  body 
resembling  a  salivary  gland  in  structure,  appearance,  and  al- 
most in  function.  It  assumes  the  form  of  a  number  of  greyish 
white  lobuli  placed  around  the  anterior  mesenteric  artery, 
moulded  in  between  the  various  structures  in  this  neigh- 
bourhood. It  is  mainly  attached  to  the  double  colon,  from 
which  it  rec[uires  careful  separation,  and  will  be  found  for 
the  most  part  on  the  right  side  of  the  spine,  which  portion 
is  termed  its  head,  and  around  which  the  duodenum  curves 
in  its  upward  course.  Its  various  lobules  give  off  ducts 
which  unite  and  reunite  to  form  finally  the  pancreatic 
duct,  which  passes  into  the  gastro-hepatic  omentum,  where 
it  unites  with  the  biliary  (or  hepatic)  duct  and  terminates  at 


THE   ABDOMEN.  225 

the  duodenum.  It  is  supplied  with  blood  from  the  coeliac 
and  anterior  mesenteric  arteries  ;  its  blood  passes  into  vena 
portse. 

The  liver  is  another  important  accessory  gland  of  diges- 
tion. It  is  that  chocolate  coloured  body  found  in  the 
anterior  part  of  the  abdomen  inclined  to  the  right  side 
lying  in  contact  with  the  diaphragm  anteriorly,  while 
the  duodenum  courses  from  below  upwards  over  its  posterior 
surface.  It  is  thickest  in  the  centre,  and  grows  gradually 
thinner  towards  its  outer  circumferent  margin.  It  is 
divided  by  deep  fissures  into  lobes,  of  which  there  are 
three  principal  and  several  accessory.  The  right  lobe  is 
the  largest,  and  is  connected  to  the  left  by  the  middle.  Its 
anterior  surface  is  smooth,  invested  by  peritoneum  ;  its 
superior  margin  presents  a  depression,  fossa  renalis,  on 
which  the  right  kidney  rests;  from  this  part  the  right 
lateral  ligament  runs,  and  superficially  through  the  supero- 
anterior  part  of  the  right  lobe,  the  posterior  vena  cava 
passes  from  the  right  side  of  the  spine  to  foramen  dex- 
trum.  The  posteror  surface  of  the  right  lobe  presents 
superiorly  a  peculiar  triangular  accessory  lobe,  the  lohus 
Spigelii  vel  caudatus.  The  external  and  inferior  margins 
are  free  while  the  inner  is  in  connection  with  the  middle 
lobe,  which  anteriorly  receives  the  falciform  and  round 
ligaments.  Posteriorly,  it  presents  the  porta  or  transverse 
fissure,  which  extends  to  the  right  and  left  lobes,  and  to  which 
the  arteries  resulting  from  division  of  the  hepatic  branch  of 
the  coeliac  axis  pass,  and  also  the  vena  portse  and  gastro- 
hepatic  omentum,  between  the  folds  of  which  the  nerves 
and  lymphatics  run,  and  also  the  hepatic  duct,  which  meets 
the  pancreatic  duct,  and  the  vessel  thus  formed  opens  into 
the  duodenum.  (There  is  no  gall-bladder  in  the  horse, 
hence  no  cystic  duct,  as  in  other  animals.)  The  inferior 
margin  of  the  middle  lobe  is  divided  by  numerous  iissures 
into  several  almost  equal  parts,  between  two  of  which  the 
round  ligament  passes  in  terminating.  This  is  the  lohus 
scissatus.  The  left  margin  of  the  middle  lobe  blends  with 
the  right  of  the  left  lobe,  to  the  superior  margin  of  which 
the  left  lateral  ligament  is  attached.  Its  other  margins  are 
regular,  and  its  surfaces  smooth.  On  carefully  examining 
the  surface  of  the  liver  we  may  see  that  it  is  _  mapped  out 
into  minute  polygonal  divisions  or  lohuli,  which  are  found 
to  be  shaped  like  an  ivy  leaf  and  consists  of  a  number  of 


226  OUTLINES    OF   EQUINE   ANATOMY. 

hexagonal  epithelial  "bile  cells"  recognizable  by  tlieir  yellow 
colour,  due  to  granular  contents.  These  acini  or  lobules 
are  embedded  in  the  sj^ecial  stroma  of  the  gland,  Glisson's 
capsule,  which  has  a  thin  layer  investing  the  surface  of  the 
organ  and  becomes  well  marked  at  the  transverse  fissure. 
The  circulation  through  the  liver  is  complex.  Vena 
portse  receives  the  blood  from  the  anterior  and  posterior 
mesenteric,  pancreatic,  splenic,  and  (lastly)  gastric  veins ;  it 
passes  through  a  ring  formed  by  the  pancreas  and  direct 
to  the  porta  of  the  liver,  during  its  whole  course  inferiorly 
placed  to  the  posterior  vena  cava.  It  enters  the  left  ex- 
tremity of  the  transverse  fissure  and  sends  a  branch  to  each 
lobe,which  breaks  up  into  vaginal  hranclies  iowiidi  in  Glisson's 
capsule,  which  divide  and  subdivide,  at  length  forming  the 
interlobular  veins,  which  ramify  on  the  surface  of  the  lobule 
sending  branches  inwards  ;  these  radiate  towards  the  centre 
of  the  lobule,  where  they  terminate  in  the  intralobular  vein, 
which  at  the  base  of  the  lobule  opens  into  a  sublobular 
vein,  in  relation  to  which  the  acinus  is  placed  as  a  sessile 
leaf  is  to  a  branch.  By  union  and  reunion  the  sublobular 
veins  at  length  form  the  hepatic  veins,  which  terminate  by 
numerous  orifices  at  the  posterior  vena  cava,  as  may  be 
exposed  by  slitting  up  in  its  interhepatic  portion.  The 
hepatic  artery  is  a  branch  of  the  coeliac  axis  ;  gives  off  a 
branch  to  the  duodenum,  which  gives  off  the  right  gastric 
artery,  and  terminates  by  breaking  up  before  arriving  at 
the  porta.  Its  mode  of  termination  with  regard  to  the  hepa- 
tic and  portal  veins  is  not  yet  known,  its  subdivisions 
have  been  traced  into  the  substance  of  the  lobuli.  The 
liver  is  supplied  with  nerve  force  by  the  sympathetic  and 
pneumogastrics. 

The  abdominal  portion  of  the  alimentary  tract  consists 
of  the  stomach  and  the  major  j)ortion  of  the  intestinal 
canal.  It  presents  three  coats,  peritoneal,  muscular,  and 
mucous.  The  peritoneal  coat  of  the  stomach  is  continued 
on  each  side  as  the  omenta ;  that  of  the  intestines  has 
been  described.  It  is  named  differently  in  different  parts. 
Thus  the  duodenum  is  supported  by  a  continuation  of  the 
gastro-hepatic  omentum,  the  remainder  of  the  small  in- 
testines by  the  mesentery,  and  the  several  j)arts  of  the  large 
intestine  by  the  mesocsecum,  mesocolon,  and  mesorectum 
respectively.  The  mesentery  is  arranged  in  a  spiral  manner 
around  the  anterior  mesenteric  artery.  In  its  free  margin, be- 


THE    ABDOMEN.  227 

tween  its  folds  lie  the  jejunum  and  tlie  ileum.  At  first  sliort, 
it  gradually  increases  in  length  until  it  gains  its  maximum, 
when  it  again  grows  short.  Between  its  folds  are  arteries, 
veins,  lacteals  (or  lymphatics),  and  nerves.  The  arteries  are 
mesenteric  hranclies,  from  thirteen  to  eighteen  in  number, 
which  pass  from  a  common  centre  and  radiate,  being  con- 
nected, forming  arches  at  the  attached  border  of  the  small 
intestine,  from  which  smaller  vessels  are  given  off,  which 
pass  to  break  up  in  supplying  the  coats  of  the  bowel.  The 
veins,  arranged  in  like  manner,  terminate  in  forming  the 
anterior  and  posterior  mesenteric  veins,  which  form  the 
commencement  portion  of  the  vena  portse.  The  nerves  are 
some  of  those  branches  of  the  sympathatic  which,  in  radi- 
ating from  the  semilunar  ganglion,  form  the  solar  plexus. 
The  lacteals  are  lymphatic  vessels,  which  being  filled  with 
an  opaque  milky  fluid,  chyle,  the  product  of  digestion,  re- 
ceive a  name  distinct  from  from  those  in  other  parts  of  the 
body.  Passing  from  the  intestinal  villi,  these  minute  vessels 
proceed  upwards  towards  the  spine  and  near  the  anterior 
mesenteric  artery  pass  through  the  mesenteric  glands,  num- 
erous greyish  nodular  bodies,  by  which  the  lacteal  fluid  is 
rendered  cellular  and  coagulable ;  they  differ  in  no  point  in 
structure  from  other  lymph-glands  of  the  body.  The  ter- 
mination of  the  lacteals  is  in  the  receptaculum  chyli,  a 
dilated  vessel  which  receives  lymph  from  the  hinder  parts 
of  the  body  and  the  chyle,  and  from  the  anterior  part  of 
which  the  thoracic  duct  runs  forwards  and  serves  to  convey 
the  fluid  into  the  venous  circulation.  This  cavity  has  very 
thin  transparent  walls,  and  is  situated  between  the  anterior 
mesenteric  artery  and  the  coeliac  axis,  in  which  situation  also 
we  may  find  the  semilunar  ganglion,  the  largest  ganglion 
in  the  body,  to  which  the  splanchnic  and  part  of  the  pneumo- 
gastric  nerves  pass,  and  from  which  plexus  run  with  the 
branches  of  the  coeliac  axis,  anterior  and  posterior  mesen- 
teric, and  renal  arteries  receiving  their  names  after  the  ar- 
teries they  surround.  Those  in  the  mesentery  form  the 
solar  plexus.  Branches  run  backwards  to  the  hypogastric 
plexus. 

The  peritoneal  coat  of  the  double  colon  is  reflected  from 
the  under  surface  of  the  loins  and  covers  at  once  both  the 
diverging  and  returning  portions,  so  that  they  are  con- 
tained in  a  common  serous  covering  terminating  in  a  blind 
extremity  at  the  sigmoid  flexure.     That  portion  between 


228  OUTLINES    OF   EQUINE    ANATOMY. 

the  two  divisions  of  the  intestine,  wHcli  is  most  marked  at 
the  sigmoid  flexure,  is  termed  the  mesocolon.     It  presents 
the  figure  of  a  racket  bat,  the  broad  portion  of  which  is  at 
the  sigmoid  flexure.     The  diverging  portion  of   the  double 
colon  is  also  attached  to  the   caecum  by  a  double  fold  of 
peritoneum,  the  mesocsecum,  while  the  single  colon  floats 
atvthe  free  margin  of  a  double  peritoneal  fold,  which,  after 
being  continued  for  a  slight  distance  posteriorly  around  the 
anterior  ^^art  of  the  rectum  (the  mesorectum),  is  reflected  la- 
terally on  to  the  walls  of  the  abdomen  in  forming  the  anterior 
boundary  of  the  pelvis.    In  the  large,  as  in  the  small  intes- 
tine, we  find  the  arteries  forming  loops  between  the  peritoneal 
supporting  layers  from  which  branches  run  to  the  attached 
margin  of  the  intestine,  where  they  break  up  in  supplying 
mainly  the  muscular  and  the  mucous  coats.    The  csBcum  is 
supplied  by  two  branches  of  the  anterior  mesenteric  artery. 
They  run  towards  its  apex  and  anastomose  just  before  reach- 
ing it ;  they  send  off  numerous  branches.  The  double  colon 
is  supplied  by  two  branches  from  the  anterior  mesenteric, 
which  run  along  the  attached  margins  of  the  diverging  a,nd 
returning  portions  respectively,  and   anastomose  on  con- 
verging at  the  sigmoid  flexure.  A  branch  from  the  anterior 
mesenteric  also  passes  to  the  anterior  part  of  the  single 
colon,  and  posteriorly  joins  the  first  branch  of  the  pos- 
terior mesenteric,  which  breaks  up   in  the   mesorectum, 
forming  arched  vessels  which  supply  the  single  colon  and  the 
anterior  part  of  the  rectimi,  anastomosing  posteriorly  with 
the  hsemorrhoidal  branches  of  the  lateral  sacral,  by  which, 
in  conjunction  with  branches  of  thp,  artery  of  the  bulb,  the 
posterior  part  of   the  rectum  and  the  anus  are  supplied. 
The  veins  of  the  large  intestine  converge  to  form  the  an- 
terior   and   posterior   mesenteric   veins,   which  form   the 
commencement  of    vena   portae,  up   against   the  anterior 
mesenteric  artery.     The  7ierve  siipijly  of  the  large  intestine 
is  conveyed  by  branches  from  the  semilunar  and  posterior 
meseiiteric  ganglia.      The  latter  is  found  in  contact  with 
the  artery  of  the  same  name,  and  sends  fibres  in  a  back- 
ward direction,  which  combine  to  form  an  intricate  arrange- 
ment of  nerve-fibres  of  the  walls  of  the  rectum  in  the  pelvis, 
to  which  the  name  hypogastric  ])lexus  is  given.     Numerous 
lymphatic  or  lacteal  glands  may  be  seen  in  apposition  with 
the  attached  portions  of  the  large  intestine  along  its  whole 
length,  but  ^predominating  in  the  anterior  part.    The  vessels 


THE   ABDOMEN.  229 

from  thence  pass  towards  the  spine  to  empty  themselves  into 
the  receptaculum  chyli. 

The  stomach,  somewhat  small  in  the  horse  as  compared 
with  other  animals,  is  found  mainly  in  the  left  hypochondriac 
region  of  the  abdomen.  It  however  extends  into  the  epi- 
gastric, and  sometimes  into  the  right  hypochondrium  under 
extreme  distension.  It  is  likened  to  the  bag  of  a  bagpipe, 
and  from  this  it  may  be  seen  that  it  is  a  somewhat  elon- 
gated body,  curved  upon  itself,  having  two  extremities. 
To  one  of  these  extremities,  that  placed  on  the  left  side 
and  most  superiorly,  in  contact  with  the  posterior  surface 
of  the  diaphragm,  the  oesophagus  passes  after  emerging 
through  foramen  sinistrum.  It  is  surrounded  by  a  fold 
of  peritoneum,  which  is  designated  the  cardiac  ligament, 
which  posteriorly  ex^^ands  over  the  stomach,  while  to  the 
left  it  forms  an  omentum  which  serves  to  connect  the 
stomach  to  the  diajphragm,  and  is  termed  the  gastro- 
phrenic oinentum.  This  extremity  of  the  stomach  is  termed 
the  left  or  cardiac,  while  from'  the  right  or  pyloric  ex- 
tremity the  small  intestine  commences.  That  margin  of 
the  organ  situated  between  these  two  extremities,  and 
which  is  most  superiorly  placed,  passing  in  an  oblique 
direction  from  left  to  right  and  from  above  downwards, 
is  termed  the  lesser  curvature,  and  from  it  the  gastro- 
hepatic  omentum  runs  to  the  porta  of  the  liver,  and  on 
the  right  side  extends  to  the  spine,  having  the  duodenum 
between  its  layers  at  the  free  margin,  to  which  the  duct 
formed  by  combination  of  the  excretory  vessels  of  the 
pancreas  and  liver  runs,  almost  directly  from  the  liver  to 
the  bowel,  into  which  it  opens  about  four  inches  from  the 
pylorus,  on  the  free  margin,  having  wound  round  the 
intestine  for  that  purpose.  The  two  extremities  of  the 
stomach  being  attached  to  the  upper  wall  of  the  abdomen, 
the  greater  curvature  of  the  stomach  is  situated  below 
and  behind  the  lesser  in  such  a  manner  that  the  organ 
being  obliquely  placed  from  above  downwards  from  left 
to  right,  as  well  as  from  before  to  behind,  presents  a  j^os- 
tero -superior  and  an  antero -inferior  surface,  both  of  which 
are  covered  by  layers  of  peritoneum,  which  at  the  greater  cur- 
vature form  omenta.  Thus,  to  the  left  extremity  is  attached 
the  spleen  by  the  gastro- splenic  omentum,  while  to  the 
greater  part  of  the  greater  curvature  the  gastro-colic  omen- 
tum is  attached,  and,  by  running  in  a  backward  direction, 


280  OUTLINES    OF   EQUINE   ANATOMY. 

and  then  again  forwards,  and  forming  a  covering  for  part 
of  the  double  colon,  produces  a  peculiar  cavity  of  serous 
membrane,  connected  to  the  main  cavity  by  a  channel  up 
against  the  anterior  mesenteric  artery,  which  has  received 
the  name  of  foramen  of  Winslow.  In  the  gastro-colic  or 
or  omentum  major,  we  sometimes  find  much  fat.  By 
butchers  it  is  termed  the  "  caul.'' 

The  stomach  of  the  horse  presents  a  rounded  cul-de-sac 
at  its  left  extremity,  more  marked  than  in  most  other 
animals.  It  has  a  muscular  and  a  mucous  coat  in  addition 
to  the  peritoneal  already  described.  The  muscular  coat, 
centrally  placed  between  the  serous  and  mucous  layers, 
presents  three  lasers  of  fibres :  longitudinal,  most  marked 
along  the  lesser  curvature,  continuous  with  those  of  the 
oesophagus  and  duodenum  at  their  extremities  ;  oblique, 
which  predominate  at  the  left  extremity  ;  and  circular,  con- 
tinuous with  those  of  the  oesophagus  and  duodenum,  ex- 
tending over  the  whole  surface  of  the  viscus,  and  which 
centrally  by  their  contraction  seem  sometimes  to  practically 
divide  it  into  two  compartments. 

The  mucous  layer  is  divided  into  two  parts,  cuticular 
and  villous.  These  two  portions  present  a  sharp  line  of  de- 
marcation, which  is  sigmoid.  The  former  occupies  about  the 
left  third  of  the  inner  surface  of  the  stomach,  and  is  ana- 
logous with  the  mucous  membrane  of  the  three  first  com- 
partments of  the  stomach  of  the  ruminant,  for  it  is  directly 
continuous  with  that  of  the  oesophagus,  being  whiter  and 
more  firm  than  that  forming  the  villous  portion,  which  is 
reddish  in  colour,  slimy  in  nature,  and  occupies  the  left 
two  thirds  of  the  stomach,  being  continuous  through  the 
pyloric  opening  with  that  of  the  duodenum.  Upon  exa- 
mination under  the  microcsope  we  may  distinguish  in  this 
portion  glandular  follicles  or  peptic  glands,  the  deeper 
portions  of  which  are  lined  by  spheroidal  epithelium,  and 
which  secrete  the  gastric  juice,  in  addition  to  those  mucous 
follicles  lined  by  tessellated  epithelium,  which  secrete 
mucus,  and  are  apparent  also  in  the  cuticular  portion. 
To  the  cuticular  portion  we  sometimes  find  bots  (oestrus 
equi)  adhering,  rarely  to  the  villous.  The  left  extremity 
of  the  stomach  comes  in  apposition  with  the  pancreas,  dia- 
phragm, left  kidney,  and  left  pre-renal  capsule.  All  the 
branches  of  the  coeliac  axis  supply  this  organ  ivith  blood. 
The  gastric  (centrally  situated)  runs  direct  to  the  centre 


THE   ABDOMEN.  231 

of  the  lesser  curvature,  where  it  breaks  up  in  forming  the 
superior  and  inferior  gastric  artefi'ies,  which  run  to  the  sur- 
faces of  the  same  name.  The  splenic,  inclining  to  the  left, 
passes  between  the  layers  of  the  gastro-splenic  omentum, 
sending  branches  outwards  to  the  spleen,  inwards  to  the 
stomach,  and,  after  gaining  the  apex  of  the  spleen,  it  con- 
tinues along  the  greater  curvature  as  the  left  gastric  artery. 
The  hepatic,  running  to  the  right  side  to  gain  the  porta  of 
the  liver,  sends  a  branch  to  the  duodenum,  which,  on  gain- 
ing the  intestine,  sends  a  branch  backwards  to  anastomose 
with  the  first  mesenteric  branch  of  the  anterior  mesen- 
teric trunk,  and  one  forwards  to  be  continued  beyond 
the  pylorus,  over  the  right  extremity  of  the  greater  cur- 
vature, forming  the  rigid  gastric  artery.  All  these  vessels 
give  off  branches  freely,  which  anastomose,  and  from  which 
the  blood  is  returned  by  the  gastric  vein,  which  is  the  last 
to  gain  vena  portse  before  it  enters  the  liver.  The  nerves 
of  the  stomach  are  derived  from  the  splanchnic  and  solar 
nerves ;  while  the  left  pneumogastric  mainly  expends 
itself  on  the  upper  surface,  the  right  runs  to  the  inferior, 
but  both  these  nerves  are  intimately  connected  with  the 
semilunar  ganglion.  For  convenience  of  reference  the 
cavity  of  the  belly  is  by  anatomists  artificially  divided 
into  nine  parts.  From  either  side  of  the  ensiform  car- 
tilage in  a  direct  line  backwards  to  the  brim  of  the  pelvis, 
and  from  the  ant ero -inferior  spinous  process  of  one  ilium 
to  the  other,  and  from  the  posterior  margin  of  the  last  rib 
to  that  of  the  other,  lines  are  drawn,  and  in  this  way  the 
cavity  is  found  to  present  anteriorly  the  epigastric  portion, 
with  the  right  and  left  hypochondriacs  on  either  side ; 
centrally,  the  umbilical  portion,  with  the  right  and  left 
lumhars  ;  posteriorly,  the  hypogastric  and  the  right  and  left 
iliacs. 

The  intestines  present  three  coats — serous,  muscular,  and 
mucous.  The  serous  coat  has  already  been  noticed  as 
part  of  the  visceral  peritoneum.  It  is  the  most  external  of 
the  coats,  and  extends  from  the  stomach  to  the  anterior 
part  of  the  rectum,  thus  leaving  the  posterior  part  of  that 
bowel  with  only  two  coats.  It  is  also  deficient  where  two 
portions  of  intestine  lie  in  close  apposition  permanently, 
or  where  organs,  as  the  pancreas,  come  into  intimate  con- 
tact with  the  intestinal  walls.  The  muscular  coat  consists 
of  two  orders  of  fibres  of  the  white,  unstriated,  or  involun- 


23-2  OUTLINES    OF   EQUINE   ANATOMY. 

tary  class.  The  internal  or  circular,  wliicli  run  round  the 
intestinal  tube,  are  found  in  all  parts  evenly  diffused  over 
the  surface  of  the  intestine,  being  anteriorly  in  direct  con- 
nection with  the  circular  fibres  of  the  stomach  at  the 
pylorus.  Posteriorly  collected  into  a  mass,  which  forms 
the  internal  portion  of  the  sphincter  ani.  The  external  w 
loncjitucli7ial  order  of  fih'es  is  evenly  diffused  over  the  surface 
of  the  small  intestine  and  of  the  rectum,  while  in  the  csecum 
and  colon  these  fibres  are  collected  into  thick  bands,  which 
run  longitudinally  to  the  course  of  the  bowel,  and  are  more 
or  less  numerous  in  different  parts.  Being  shorter  than 
the  bowel  itself,  and  at  the  same  time  intimately  attached 
to  its  walls,  they  serve  to  "  pucker"  up  its  surface  into  a 
number  of  cavities,  which  give  it  a  peculiar  appearance, 
whilst  by  division  of  the  bands  it  may  be  reduced  to  a  tube 
of  uniform  diameter  and  of  much  greater  length.  On  ex- 
posing the  bowels  of  an  animal  shortly  after  death  we  may 
observe  the  vermic2ilar  or  ^yeristaltic  action  of  the  intestines, 
that  slow  consecutive  contraction  of  their  fibres  commencing 
anteriorly  and  extending  backwards,  whereby  the  ingesta 
is  slowly  propelled  from  the  pylorus  to  the  anus.  The 
mucous  coat  of  the  bowels  is  of  a  reddish-grey  colour  and 
slimy  nature,  extends  from  the  pylorus  (where  it  is  con- 
tinuous with  the  villous  portion  of  the  gastric  mucous 
membrane)  to  the  anus,  where  it  gradually  blends  with  the 
common  integument.  It  consists  of  corium  and  basement 
membrane,  on  the  free  surface  of  which  is  columnar  epi- 
thelium, and  throughout  presents  depressions  of  this 
mucous  membrane  termed  follicles  of  Lieberhnhn,  which 
secrete  mucus,  and  prominences  of  the  same,  villi  orpapillce, 
from  the  centre  of  which  a  lacteal  commences,  either  by  a 
plexus,  loop,  or  a  blind  pouch,  for  these  are  the  portions  of 
the  intestine  from  which  the  lacteals  arise,  and,  though 
most  numerous  in  the  small  intestine,  they  may  be  found 
also  in  the  large.  Throughout  the  intestinal  tract  also  we 
find  embedded  in  the  mucous  membrane  small  bodies 
called  solitary  gkmds,  which  consist  apparently  of  a  number 
of  cells  bound  together  by  somewhat  dense  areolar  tissue, 
and  having  blood-vessels  runniog  through  them.  They 
present  no  ducts,  and  hence  are  considered  to  be  analogous 
in  nature  and  function  with  the  Malpighian  corpuscles  of 
the  spleen,  though  some  aiithorities  assert  that  by  bursting 
they  discharge  their  contents  into  the  intestine,  and  thus 


THE    ABDOMEN.  233 

give  tlie  faeces  its  peculiar  odour.  The  intestines  of  tlie 
horse  are  about  ninety  feet  in  length,  and  as  the  posterior 
eighteen  feet  are  much  larger  in  calibre  than  the  rest,  it  is 
divided  into  the  large  and  the  small  intestine.  The  small  intes- 
tine commences  from  the  pyloric  extremity  of  the  stomach, 
and  just  after  its  commencement  becomes  very  large.  It 
is  here  termed  the  duodenum,  and  takes  an  upward  direc- 
tion over  the  posterior  concave  surface  of  the  liver,  to  the 
porta  of  which  it  is  attached  by  a  continuation  of  the 
gastro-hepatic  omentum,  between  the  two  layers  of  which 
the  duct  common  to  the  liver  and  the  pancreas  runs  to  the 
attached  margin,  and  then,  after  passing  beneath  the  peri- 
toneal coat,  opens  on  the  free  margin  through  a  perforated 
papilla  into  the  intestinal  canal,  about  four  inches  from 
the  pylorus.  Passing  in  an  upward  direction,  the  duo- 
denum takes  a  curve  around  the  head  or  right  extremity 
of  the  pancreas  (termed  its  horse-shoe  curve),  and  then, 
passing  underneath  the  spine  behind  the  anterior  mesen- 
teric artery,  terminates.  The  rest  of  the  small  intestine 
occupies  no  regular  position  in  the  abdomen,  for,  being 
attached  in  the  free  margin  of  the  mesentery,  it  hangs 
loose,  but  terminates  in  the  right  lumbar  region,  where  it 
opens  into  the  large  intestine,  the  muscular  coat  being  here 
doubled  in  such  a  manner  as  to  form  the  ileo-csecal  valve, 
which  prevents  food  from  passing  from  the  large  into  the 
small  intestines  under  ordinary  circumstances.  The  ante- 
rior two  fifths  of  this  portion  of  the  small  intestine  is 
termed  the  jejumtm,  and  the  posterior  three  fifths  the 
iletmi.  This  division  is  purely  artificial,  and  anatomists 
now  prefer  to  describe  the  fixed  or  duodenal,  and  the  free 
portions  of  the  small  intestine.  The  mucous  coat  of  the 
duodenum  presents,  in  addition  to  papillae,  follicles  of 
Lieberklihn,  and  solitary  glands  (extremely  rare  here), 
certain  small  racemose  glands,  in  every  respect  resembling 
salivary  glands,  even,  it  is  supposed,  in  the  nature  of  their 
secretion,  of  which,  however,  nothing  definite  is  known, 
these  are  named  Brunner's  glands,  after  their  discoverer. 
On  the  free  margin  of  the  ileum  and  of  the  posterior  part 
of  the  jejunum  may  be  seen  elongated  patches,  apparently 
of  pigmentary  matter.  These  are  Peyer's  patches,  and 
when  examined  microscopically  are  found  to  be  aggrega- 
tions of  solitary  glands  surrounded  by  a  row  of  fol- 
licles of  Lieberklihn  termed  the  corona  tubulorum,  while 


234  OUTLINES    OF   EQUINE   ANATOMY. 

villi   may   be   seen   covering  tlie   space   enclosed  by  the 
corona. 

The  large  intestine  consists  of  three  portions  :  ccemim, 
colon,  and  rectum.  The  ileum  terminates  at  a  peculiarly 
arched  portion  of  intestine,  the  ccecuni  caput  coli,  at  its 
lesser  curvature,  anteriorly  is  the  commencement  of  the 
double  colon.  The  caecum,  a  plicated  portion  of  in- 
testine, presents  a  base  situated  in  the  right  lumbar  and 
right  iliac  regions,  from  which  it  extends  in  a  direction 
forwards  and  to  the  left,  through  the  umbilical  region  along 
the  floor  of  the  abdomen,  to  terminate  in  the  apex  in  the 
left  hypochondriac  region.  Its  plicae  are  due  to  the  collec- 
tion of  its  longitudinal  muscular  fibres  into  three  bands  at 
the  apex,  while  subsequently  a  fourth  appears.  This 
viscus  is  capable  of  containing  about  four  gallons  of  fluid, 
and  is  supposed  to  be  the  destination  of  the  huge  draughts 
of  water  sometimes  consumed  by  horses,  which  rushes 
directly  through  the  stomach  hither  ;  and  since  it  is  apt  to 
carry  with  it  any  undigested  matters,  we  learn  from  this 
the  rule  found  valuable  in  practice — "to  water  before 
feeding." 

The  colon  is  divided  into  two  portions — double  and 
single;  for  after  proceeding  a  certain  distance  the  bowel 
bends  backwards  and  returns  on  the  same  course,  becoming 
attached  to  the  diverging  portion  by  the  meso-colon,  and 
in  some  parts  closely  in  contact  with  it.  The  posterior 
part  of  the  colon,  however,  runs  a  single  course,  being 
situated  at  the  free  margin  of  the  mesorectum,  and  like 
the  free  portion  of  the  small  intestine  having  no  regular 
situation.  It  takes  the  following  course  : — Commencing  at 
the  right  lumbar  region  with  two  muscular  bands,  it  runs 
in  a  forward  direction  from  the  caecum  caput  coli  into  the 
right  hypochondriac  region,  where  it  obtains  a  third,  and 
subsequently  a  fourth  longitudinal  band ;  passing  over  to 
the  left,  above  the  ensiform  cartilage,  it  gains  the  left 
hypochondrium,  and,  in  running  from  this  backwards, 
grows  gradually  smaller  in  calibre  as  it  passes  through  the 
left  lumbar  into  the  left  iliac  region.  Its  bands  also 
decrease  in  number,  so  that  when  it  makes  its  sigmoid 
flexure  in  the  left  iliac  region  it  has  but  one,  and  that  is 
on  the  attached  margin.  The  bowel  is  here  very  small, 
though  not  so  small  as  at  its  commencement,  and  in  pass- 
ing forwards  through  the  left  lumbar  and  left  hypochon- 


THE    ABDOMEN.  235 

driac  regions,  superiorly  placed  to  the  diverging  portion,  it 
increases  in  size  and  the  number  of  its  bands  until  it  again 
reaches  the  epigastric  region,  when  it  inclines  backwards, 
it  attains  its  maximum  calibre,  and  has  three  muscular 
bands.  After  passing  into  the  umbilical  region  it  termi- 
nates in  the  single  colon,  which  has  two  muscular  bands, 
hangs  freely  in  the  free  margin  of  the  mesorectum,  being 
about  three^  feet  in  length,  until  at  the  central  line  poste- 
riorly it  terminates  in  forming  the  rectum,  which  runs 
directly  from  the  posterior  part  of  the  hypogastric  region 
to  the  anus.  Its  muscular  wall  is  very  thick  with  the 
fibres  well  marked;  superiorly  it  is  in  contact  with  the 
under  surface  of  the  sacrum  and  the  structures  about  it ; 
while  its  inferior  surface,  in  the  male,  rests  upon  the  upper 
surface  of  the  bladder,  prostate,  &c.,  and  in  the  female 
upon  the  vagina.  In  contact  with  its  walls  laterally  is  the 
hypogastric  plexus.  Its  muscular  coat  terminates  poste- 
riorly in  forming  the  inner  portion  of  sphincter  ani,  of 
which  the  external  portion  is  formed  of  dark-red  fibres, 
supplied  with  nerve-force  hy  the  posterior  part  of  the  spinal 
cord.  To  this  muscle  superiorly  is  attached  levator  ani, 
running  from  the  under  part  of  the  anterior  coccygeal 
bones.  Laterally,  retractor  ani,  from  the  inner  surface  of 
the  sacro-sciatic  ligament,  as  far  forward  as  the  ileum ; 
inferiorly,  depressor  ani,  which,  in  the  female,  blends  with 
sphincter  vaginae  ;  in  the  male  with  retractor  penis.  The 
mucous  membrane  of  the  rectum  is  continuous  posteriorly 
with  the  thin,  hairless  skin,  which  is  around  the  anus 
"  like  the  mouth  of  a  draw-purse,"  and  which  has  many 
sebaceous  glands.  Some  fat  also  enters  into  the  formation 
of  the  anus.  The  glands  and  villi  of  the  mucous  mem- 
brane gradually  decrease  in  number  from  the  csecum  to 
the  anus. 

The  spleen  is  a  peculiar  sickle-shaped  organ,  attached  to 
the  left  extremity  of  the  greater  curvature  of  the  stomach 
by  the  gastro-splenic  omentum.  Of  a  bluish  colour,  and 
about  three  pounds  in  weight ;  it  presents  a  base  and  an 
apex^  a  greater  and  a  lesser  curvature,  and  two  surfaces.  The 
hase  is  attached  up  against  the  left  kidney,  and  prerenal 
capsule,  and  from  this  the  organ  extends  in  a  downward  and 
backward  direction  and  towards  the  right  side,  gradually  de- 
creasing in  size.  The  lesser  curvature,  hilum,  is  that  situated 
nearest  the  stomach  along  which  the  vessels  of  the  organ 


236  OUTLINES    OP    EQUINE   ANATOMY. 

run ;  from  this  tlie  organ  decreases  in  thickness  towards 
the   greater  or  free  curvature,    around    which   the   serous 
membrane  is  reflected  joining  the  layers  on  the  surfaces  ; 
the  curvatures  meet  at  the  apex.     The  special  ca29s^^Ze  oftlie 
spleen  consists  mainly  of  yellow  elastic  tissue,  whereby  it  is 
endowed  with  great  capacity  of  distension,  for  it   is  an 
erectile  organ.     From  this    outer   covering   trabecules    or 
septa  project  inwards  in  all  directions,  thus  dividing  the 
organ  into  spaces  which  contain  a  peculiar  reddish  matter, 
spleen  pulp,  ai^tly  compared   to  raspberry  jam.     On   ex- 
amination under  the  microscope  this  is  found  to   consist 
essentially  of  large  cells,  each  containing  one  or  more  red 
cells,  in  a  more  or  less  advanced  state  of  disintegration, 
for  it  is   supposed  that  the  spleen  is  the  organ  whereby 
excess  of  red  corpuscles  in  the  blood  is  prevented.     The 
spaces  between  the  trabeculse  also  contain    vessels.     The 
arteries,  derived  from  the  splenic  branch  of  the  coeliac  axis, 
terminate  in  venous  sinues,  and  are  also  remarkable  for  pre- 
senting at  various  intervals,  embedded  in  their  fibro-areolar 
coat,  small  bodies  analogous  in  structure  to  the  solitary 
glands  of  the  intestines.  These  are  Malpighian  corpuscles, 
the  use  of  which  is  not  known,  and  which  consist  of  aggre- 
gations of  cells  embedded  in  a  fibrous  stroma.     The  veiiis  of 
the  spleen  commence  from  the  venous  sinuses,  they  have 
few  if  any  valves,  and  pour  their  contents  into  the  vena 
portse.     The  nerves  of    the  spleen  are  derived  from  the 
semilunar  ganglion.  The  prerenal  capsule  is  another  organ 
the  use  of  which  is  undetermined.     There  is  one  on  either 
side  of  the  body,  situated    between  the  kidney  and  the 
spine,  and  presenting  two  surfaces.     It  derives  its  blood 
by  a  special  arterial  branch,  either  from  the  posterior  aorta 
or  from  the  renal  arteiy.  When  cut  into  it  presents  an  ex- 
ternal dark,  or  cortical  portion,  the  use  of  which  is  unknown  ; 
and  a  central  lighter  medullary  part,  supposed  to  be  a  nerve 
centre.     It  is  included  among  the  ill-understood  ductless 
or  vascular  class  of  glands. 

Having  removed  the  alimentary  viscera  from  the  belly 
we  are  enabled  to  examine  the  structures  situated  in  the 
upper  part  of  the  cavity.  On  the  central  line  we  see  im- 
portant vessels  and  nerves.  The  posterior  aorta,  after 
passing  through  hiatus  aorticus  of  the  diaphragm  in 
company  with  the  thoracic  duct  and  vena  azygos,  runs 
backwards,  inclined  to  the  left  side  of  the  spine.     In  its 


THE    ABDOMEN.  287 

course  it  gives  off  important  vessels.  Coeliac  axis,  a  single 
trunk,  is  but  a  short  vessel,  for  it  soon  breaks  up  into 
three  branches,  gastric,  splenic,  and  hepatic.  The  gastric 
runs  direct  from  its  commencement  to  the  central  part  of 
the  lesser  cui-vature  of  the  stomach,  where  it  breaks  up  in 
forming  the  superior  and  inferior  gastric  arteries.  The 
splenic  inclining  to  the  left  side  and  gaining  the  base  of 
the'  spleen  runs  along  its  lesser  curvature  between  the  two 
folds  of  peritoneum  which  constitute  gastro-splenic  omen- 
tum. During  its  course  it  gives  off  large  branches  to  the 
spleen,  smaller  branches  to  the  stomach,  and  at  the  apex 
of  the  spleen  is  continued  along  the  greater  curvature  of 
the  stomach  as  the  left  gastric  artery.  The  hepatic  artery, 
which  inclines  to  the  right  side,  has  already  been  de- 
scribed. 

Anterior  mesenteric  artery  (in  the  ass  extremely  liable  to 
aneurism  from  the  presence  of  parasites  of  the  nematode 
class — strongylus  armatus)  arises  from  the  under  part  of 
the  posterior  aorta.  It  gives  off  a  few  branches  to  the 
pancreas  which  completely  surrounds  it.  And  then  the 
branches  :  mesenteric,  thirteen  to  eighteen  in  number, 
which  radiate  through  the  mesentery  to  the  small  intestine  ; 
the  first  anatomoses  with  the  duodenal  branch  of  the 
hepatic,  the  last  with  the  ccecal  branch,  which  in  its  turn 
communicates  with  the  tranches  to  the  double  colon,  and 
they  with  that  to  the  single  colon,  which  joins  the  first 
branch  of  the  posterior  mesenteric  artery,  a  vessel 
supplying  the  single  colon  and  rectum  in  a  manner  already 
described  ;  it  arises  from  the  under  surface  of  the  posterior 
aorta  just  prior  to  its  termination. 

Renal  arteries  arise  from  the  lateral  part  of  the  posterior 
aorta  just  behind  the  anterior  mesenteric  trunk.  They  are 
large  vessels,  given  off  at  right  angles.  They  are  also 
termed  the  emulgent  arteries,  and  before  arriving  at 
the  kidneys  break  up,  sometimes  sending  a  branch  to  the 
prerenal  capsule  (which  sometimes  arises  from  the  posterior 
aorta).  Most  of  their  branches  enter  the  kidney  at  a 
particular  notch,  in  its  substance  termed  the  hilum,  some 
run  to  other  parts  of  the  organ.  The  inclination  of  the 
posterior  aorta  to  the  left  side  of  the  spine  renders  the 
right  renal  artery  the  longest,  for  it  has  to  pass  under  the 
posterior  vena  cava.  It  is  also  given  off  more  anteriorly  than 
the  left. 


238  OUTLINES    OF    EQUINE    ANATOMY. 

The  spermatic  artery  is  given  off  from  the  posterior 
aorta,  between  the  commencement  of  the  renal  and  the  pos- 
terior mesenteric  vessels.  It  is  remarkable  for  its  length 
in  proportion  to  its  size,  and  for  the  convoluted  manner  in 
which  it  runs  through  the  spermatic  cord.  It  runs  in  a 
downward  and  backward  direction  to  the  internal  ab- 
dominal ring,  where  it  gains  the  spermatic  cord,  in  the 
anterior  part  of  which  it  passes  much  curled  upon  itself.  On 
getting  near  the  testicle  it  sends  off  small  long  branches 
to  the  commencement  portion  of  the  vas  deferens,  and  on 
gaining  the  antero-superior  part  of  the  organ  divides  into 
two  parts,  one  of  which  runs  in  a  backward  direction,  the 
other  downwards  until  it  gams  the  inferior  margin,  when 
it  also  curves  backwards.  Both  of  these  divisions  send 
branches  into  the  substance  of  the  organ  which  help  to 
form  the  tunica  vasculosa.  Sometimes  the  artery  of  the 
cord  is  given  of£  from  the  posterior  aorta  (often  from  the 
external  iliac).  It  runs  to  the  posterior  part  of  the  cord, 
supplying  the  cremaster  and  vas  deferens.  These  vessels 
are  arranged  as  above  described  in  the  male,  but  in  the 
female  the  ovarian  artery  takes  the  place  of  the  spermatic, 
being  much  shorter  and  smaller  in  every  respect.  These 
conditions,  however,  are  reversed  in  the  uterine  artery, 
which  much  exceeds  its  analogue  the  artery  of  the  cord  in 
size,  especially  during  pregnancy.  It  runs  downwards  and 
backwards  towards  the  pelvis  between  the  two  folds  of 
peritoneum  which  constitute  the  broad  ligaments  of  the 
uterus. 

From  its  upper  surface  the  abdominal  portion  of  the 
posterior  aorta  gives  off  the  lumbar  arteries,  which  passing 
upwards,  give  branches  to  the  psoae  muscles,  others  to 
the  muscles  on  the  loins,  the  medullary  arteries  to  the 
lumbar  vertebrae,  and  the  arteries  to  the  lumbar  por- 
tion of  the  spinal  cord.  Then  the  posterior  aorta  gives 
off  the  external  iliac  arteries  in  an  outward  direction, 
whereby  it  is  much  reduced  in  calibre,  and  under  the 
second  sacral  bone  it  terminates  in  forming  the  internal 
iliacs,  and  sometimes  the  middle  sacral,  the  former 
running  downwards  and  outwards,  the  latter  directly  back- 
wards. On  the  right  side  of  the  posterior  aorta  runs  the 
posterior  vena  cava ;  it  commences  beneath  the  anterior 
part  of  the  under  surface  of  the  sacrum,  resulting  from  the 
convergence  of  the  common   iliac  veins,  and  in  passing 


THE    ABDOMEN.  239 

forwards,  receives  sorae  veins  corresponding  to  arteries 
given  off  by  its  companion  YQS,s,Q\,spermaticvein, posterior  luni' 
har  veins  (anterior  Imnhar  veins  combine  to  form  vena  azygos) 
and  renal  veins.  Of  the  renal  veins,  the  left  is  the  longest, 
but  the  right  anteriorly  placed,  and  shortly  after  receiving 
this  vessel  the  post  vena  cava  passes  through  its  sjDecial 
channel  in  the  upper  part  of  the  right  lobe  of  the  liver. 
While  passing  through  this  it  presents  the  oj^enings,  num- 
erous and  varying  in  size,  of  the  hepatic  veins,  and  on 
emerging,  is  surrounded  by  the  coronary  ligament  in  its 
short  course  to  foramen  dextrum,  where  it  receives  the 
plirenic  venous  sinuses,  and  then  runs  straight  through  the 
chest,  enveloped  in  a  special  fold  of  pleura  to  the  base  of  the 
heart. 

On  removing  the  peritoneum  from  the  lateral  parts 
of  the  upper  surface  of  the  abdomen,  we  find  that  it 
simply  covers  the  under  surface  of  the  kidneys,  from 
which  it  is  separated  by  a  quantity  of  fat,  unusually 
firm  in  consequence  of  the  predominance  of  stearin  in 
its  composition.  This  is  vulgarly  named  "suet,"  and 
by  some  anatomists  has  been  termed  the  tunica  adiposa 
renalis. 

The  kidneys  are  the  organs  which  serve  to  separate  urine 
from  the  blood.  They  are  two  purple-coloured  organs 
situated  up  against  the  crura  of  the  diaphragm.  The 
right  is  most  anteriorly  placed,  and  differs  from  its  fellow 
in  being  heart-shaped,  and  resting  against  the  diaphragm, 
and  in  a  special  depression  on  the  upper  part  of  the  right 
lobe  of  the  liver  termed  the  fossa  re7ialis.  The  left  kidney 
is  elongated  from  behind  forwards,  being  shaped  like  a 
"kidney-bean."  It  receives  the  shortest  artery  and  the 
longest  vein,  and  lies  in  contact  with  the  base  of  the  sj^leen 
and  with  the  left  extremity  of  the  stomach.  Both  kidneys 
have  a  prerenal  capsule  in  contact  with  the  anterior  part 
of  their  inner  border  which  presents  a  notch  or  hilum,  to 
which  most  of  the  branches  of  the  renal  arteries  pass,  and 
from  which  those  of  the  renal  vein  together  with  the  ureter 
commence.  The  anterior  part  of  the  kidney  is  slightly  the 
largest,  the  outer  margin  convex,  the  inner  straight,  while 
the  under  surface  is  flatter  than  the  upper.  The  organ  is 
supported  by  a  special  stroma  {renal  capsule)  which  is  con- 
siderably more  abundant  in  the  substance  of  the  organ, 
investing  its  vessels,  and   connecting  together  its   com- 


240  OUTLINES    OF    EQUINE    ANATOMY. 

ponent  structures.  A  horizontal  incision  displays  centrally 
a  cavity  lined  with  mucous  membrane,  pelvis.  Externally  a 
reddish-mottled  smooth  surface,  cor?fzcaZjJorh'o%,  andbetween 
the  two,  the  medullary  ijortion,  which  is  apparent  to  the 
naked  eye  as  consisting  of  tubular  fibres,  radiating  from 
the  central  cavity  to  the  cortical  portion.  By  microscopic 
examination  we  may  find  that  these  tubes,  hibuli  uriniferi^ 
are  continued  into  the  cortical  portion,  when  they  be- 
come much  convoluted,  forming  the  tuhidi  contorti,  and 
finally  terminate  in  blind  dilated  extremities,  Malijigliian 
capsules. 

The  branches  of  the  renal  arteries  after  division  and 
subdivision  by  traversing  the  medullary  part,  and  breaking 
up  in  their  course  gain  the  cortical  portion,  where  as  small 
afferent  vessels  they  run  to  the  Malpighian  corpuscles  of 
which  they  push  the  mucous  membrane  before  them,  caus- 
ing it  to  bulge  towards  the  commencement  of  the  tubulus 
uriniferus,  for  they  exert  their  pressure  at  a  point  opposite 
to  this.  On  entering  the  depression  of  the  wall  of  the  cor- 
puscles thus  produced,  the  vessel  breaks  up  into  smaller 
branches,which  divide  and  reunite  producing  the  glomerulus 
or  Malpighian  tuft,  from  which  arises  the  efferent  vessel, 
which  emerges  from  the  depression  at  the  point  where  the 
afferent  vessel  enters,  and  then  runs  to  the  wall  of  the 
contorted  portion  of  the  uriniferous  tube,  around  tvJiich  it 
forms  a  plexus  of  capillaries,  from  which  veins  arise,  and 
after  passing  through  the  medullary  portion  of  the  kidney 
by  union  and  reunion,  combine  to  form  the  renal  vein. 
The  tubuli  uriniferi  in  the  medullary  portion,  in  their 
course  from  the  cortical  portion  to  the  pelvis,  unite  two 
by  two  (dichotomously),and  as  this  occurs  frecjuently,  the 
whole  of  the  tubes  opening  by  one  perforation  into  the 
pelvis  may  be  represented  by  a  pyramid,  the  base  of  which 
is  at  the  cortical  portion,  the  apex  at  the  pelvis,  and  in  the 
foetal  colt  the  kidney  is  lobulated,  divided  into  the  ''pyra- 
mids of  MaljngJii,"  while  the  same  condition  obtains  per- 
manently in  the  ox.  The  pelvis  of  the  kidney  of  the  horse 
is  a  fan-shaped  cavity  lined  by  spheroidal  epithelium,  and 
around  its  convex  border  a  ridge  extends  on  to  which  the 
uriniferous  tubes  open.  This  ridge  terminates  laterally  in 
cavities  termed  calyces  of  the  pelvis,  while  at  the  hilum  the 
pelvis  is  continuous  with  the  ureter.  This  is  a  musculo- 
membranous  canal  extending  along  the  roof  of  the  abdo- 


THE    AB'JOMEN.  241 

men,  downwards,  outwards,  and  backwards  to  the  pelvis, 
where  it  terminates  at   the  supero-posterior  part  of  the 
bladder.     It  first  passes  through  the  muscular  coat  of  that 
organ,  and  after  running  for  a    short  distance    between 
this  and  the  mucous  coat,  penetrates  the  latter,  and  thus 
distension  of  the  bladder  serves  more  securely  to  prevent 
reflux  of  urine  upon  the  kidneys.     It  presents  a  muscular 
coat,  with  an  external  layer  of  longitudinal,  and  an  internal 
layer  of  circular  fibres,  and  is  lined  with  mucous  memhrane 
which  presents  epithelial  cells  of  the  spheroidal  character. 
The  ureters  run  between  the  two  layers  of  the  broad  liga- 
ments of  the  bladder,  and  hence  are  by  some  anatomists 
described  as  having  an  external  serous  coat.     The  bladder 
is  situated  in  the  lower  part  of  the  pelvis,  and  is  a  pyri- 
form  organ,  rounded  anteriorly,  terminating  posteriorly  in 
becoming  constricted  to  form  the  nech.     The  anterior  por- 
tion is  the  fundus,  and  the  portion  between  the  fundus 
and  the  neck  is  the  hody.     Superiorly  it  is  in  contact  in 
the  female  with  the  vagina  and  the  uterus,  with  the  rec- 
tum in  the  male  ;  while  on  either  side  from  before  back- 
wards run  a  vesicula  seminalis  and  a  vas  deferens.     The 
under  surface  rests  upon  the  upper  concave  surface  of  the 
j)ubic  portion  of  the  ossa  innominata.  The  fundus  presents 
a  remarkable  puckering,  the  result  of  the  change  which 
the  bladder  undergoes  after  birth,  whereby  it  gradually 
decreases  in  proportionate  size,  and  tends  to  retract  from 
the  umbilicus  into  the  pelvis,  from  which  it  extends  into 
the  abdomen  in  a  degree  varying  with  its  plenitude.     To 
the  fundus  run  the  round  ligaments  of  the  bladder,  which 
diverge  at  an  acute  angle  and  run  forwards  and  outwards, 
enclosed  in  the   double  folds  of  peritoneum  forming  the 
hroad  ligaments,  towards  the  umbilicus.     The  fundus  also 
receives  a  coating  of  peritoneum  which  forms  a  small  cap  for 
it,  extending  farthest  backwards  superiorly  and  presents 
double  folds  runnmg  in  various  directions ;  thus  longitu- 
dinally forwards  the  falciform  or  suspensory  ligame7it  yvlus  to 
the  umbilicus.     Laterally,   the  broad  Ugamerits  (with  the 
round  ligaments  in  their  free  margins)  to  the  walls  of  the 
cavity,  and  superiorly  a  longitudinal  fold,  vesico-rtctal  fold 
in  the  male,  vesico -vaginal  in  the  female.     The  vesico-rectal 
fold  is  bounded  laterally  by  the  vasa  deferentia,  and  encloses 
the  third  vesicula  seminalis  between  its  layers.     The  ureters 
pass  to  the  supero-posterior  part  of  the  bladder,  and  open 

IG 


2i2  OUTLINES    OF    EQUINE    ANATOMY. 

into  it  in  the  peculiar  manner  already  described.  Tlie 
organ  presents  tiuo  coats — muscular  arid  mucous.  When  it 
is  distended,  the  mucons  coat  may  he  seen  between  the  mus- 
cular fibres,  which  seem  to  be  irregiilarly  arranged,  but  they 
present  a  species  of  oblique  arrangement  on  closer  inspec- 
tion, forming  what  is  termed  detrusor  urinw,  while  towards 
the  neck  of  the  bladder  they  tend  to  assume  the  circular 
form,  producing  the  sphincter  vesicce.  The  mucous  coat 
lines  the  bladder  throughout,  and  is  continuous  with  that 
of  the  ureters,  and  with  that  of  the  urethra ;  it  presents- 
thick  and  viscid  epithelium,  which  serves  to  protect  the 
organ  from  the  irritant  action  of  the  urine,  and  much  of 
which  is  expelled  with  that  fluid. 

The  urethra  is  a  membranous  elongated  passage,  com- 
mencing at  the  neck  of  the  bladder  and  running  in  a 
backward  direction  as  far  as  the  ischial  arch,  around  which 
it  winds,  and  then  runs  in  a  forward  direction  forming  the 
central  part  of  the  penis,  to  between  the  symphysis  pubis 
and  the  umbilicus.  It  consists  of  a  mucous  membrane, 
which  extends  throughout,  and  in  some  parts  presents  large 
mucous  crijpts  or  lacunoe,  which  also  communicates  with 
that  hning  the  bladder,  ejaculatory  ducts,  prostatic,  and 
Cowper's  ducts,  and  with  the  lining  layer  of  the  prepuce. 
It  is  divided  into  three  ^ovtiows,,  prostatic,  membranous,  and 
spongy.  The  prostatic  portion  is  the  shortest,  and  is  sur- 
rounded by  the  prostate  gland.  It  commences  at  the  neck 
of  the  bladder  and  passes  to  the  membranous  portion. 
Its  mucous  membrane  presents  at  its  upper  part  two  pecu- 
liar prominences  perforated  by  two  foramina,  the  openings 
of  the  ejaculatory  ducts  formed  by  union  of  the  vasa 
deferentia  and  of  the  ducts  from  the  vesiculae  seminales. 
This  prominence  is  the  veru  montanum  or  caput  cjallina- 
ginis.  On  either  side  also  may  be  seen  a  row  of  small 
papillae,  on  to  which  open  the  prostatic  ducts.  The  mem- 
branous portion  extends  from  the  prostatic  as  far  back- 
wards as  the  ischial  arch,  and  on  its  postero-lateral  parts 
are  two  rounded  bodies  about  the  size  of  a  walnut.  These 
are  Coivpers  glands,  and  like  this  jDortion  of  the  canal 
they  are  invested  by  a  portion  of  muscle,  Wilson's  muscle, 
the  fibres  of  which  run  transversely  above  the  canal  from 
one  side  to  the  other.  Like  the  prostatic  their  ducts  oj)en 
upon  numerous  small  papillse  arranged  in  rows,  one  on 
each   side  of    this  portion  of   the  urethral  canal.      The 


THE    ABDOMEN.  243 

spongy  portion  is  completely  invested  by  tlie  corpus  spon- 
giosum of  the  penis,  and  anteriorly  dilates,  forming  the 
widest  joortion  or  fossa  navicularis,  prior  to  terminating  in 
its  narrowest  ]jortion,  meatus  urinarius  extermis.  A  catheter 
which  will  pass  through  here  will  pass  along  any  portion 
of  the  canal,  unless  obstructed  by  foreign  matter. 

The  prostate  gland  is  a  body  which  embraces  superiorly 
and  laterally  the  neck  of  the  bladder.  It  is  divided  into 
two  lateral,  and  a  connecting  isthmus  or  middle  lohe.  This 
gland  is  racemose  in  its  nature,  and  pours  its  secretion 
through  the  above  described  openings  into  the  urethra. 
Cowper's  glands  are  two  in  number,  and  are  covered  by 
Wilson's  muscle  ;  they  resemble  the  prostate  in  structure. 
The  function  of  these  glands  is  but  little  known.  Their 
secretion,  by  mixing  with  the  semen,  is  considered  to  in- 
crease its  efficacy.  The  prostate  gland  hides  from  view 
the  terminal  portion  of  the  vas  deferens,  and  of  the  duct 
of  vesicula  seminalis  and  the  ejaculatory  duct. 

The  penis  is  a  dense  elongated  organ  extending  from 
the  posterior  part  of  the  ischium  in  a  forward  direction 
under  the  symphysis  of  the  ossa  innominata.  It  is  mainly 
composed  of  the  corpus  cavernosum.  This  is  situated 
at  the  superior  part,  and  presents  a  supero-lateral  surface, 
rounded  and  covered  by  a  plexus  of  veins,  an  inferior  sur- 
face concave  forming  a  groove  through  whrch  the  urethra 
(spongy)  runs,  surrounded  by  corpus  spongiosum.  Ante- 
riorly it  presents  two  sharp  points,  which  are  concealed  by 
the  glans  penis;  posteriorly,  by  bifurcation,  it  produces 
the  crura,  dense,  yellowish,  fibrous  bands  running  to  be- 
come attached  to  the  tuberosities  of  the  ischium,  which  are 
surrounded  by  the  erectores  penis  muscles,  arising  from 
the  tuberosities  of  the  ischium  and  becoming  inserted  into 
the  root  of  the  penis.  On  transverse  section  this  organ 
will  be  found  to  present  a  tendency  to  division  into  two 
parts.  It  has  externally  a  thick  layer  of  yellow  elastic 
tissue,  from  which  trabeculae  and  bands  are  sent  inwards, 
which,  by  their  union  and  reunion,  produce  spaces,  which 
are  occupied  by  venous  sinuses.  The  most  remarkable  of 
these  septa  projects  from  the  central  line  at  the  superior 
part.  It  consists  of  a  number  of  bands  running  down- 
wards, resembling  in  arrangements  the  teeth  of  a  comb, 
septum  pectiniforme. 

The  penis  anteriorly  receives  blood  from  the  external 


244  OUTLINES    OF    EQUINE    ANATOMY. 

puclic  artery,  whicli  sends  a  brancli  backwards  along  the 
upper  surface  of  the  organ  to  meet  the  anterior  hranch  of 
the  internal  pudic,  which  also  gives  off  a  branch  backwards 
to  gain  the  artery  of  the  bulb.  Immediately  investing 
the  surface  of  the  urethra,  situated  in  the  inferior  groove 
of  corpus  cavernosum,  is  corpus  spongiosum,  a  thin  layer 
consisting  of  erectile  tissue  analogous  to  that  found  in 
the  hard  palate  serving  to  connect  the  mucous  membrane 
to  the  bony  palate.  Thus  it  consists  of  a  network  of 
elastic  tissue,  through  which  blood-vessels  ramify,  and 
which  sometimes  presents  venous  sinuses.  Posteriorly, 
against  the  crura,  it  forms  a  small  dilatation  termed  the 
bulb,  which  is  covered  by  erectores  penis.  Posteriorly 
it  forms  a  large  prominent  portion,  glans  penis,  which, 
under  erection,  assumes  the  shape  of  the  extremity  of  a 
trumpet.  It  completely  covers  the  anterior  portion  of  the 
corpus  cavernosum,  and  around  its  outer  circumferent 
margin  is  a  row  of  glands,  corona  glanclis,  which  secrete  a 
sebaceous  material.  It  is  covered  by  a  highly  sensitive 
mucous  layer,  and  at  its  centre,  inclined  to  the  lower  part, 
presents  a  deep  depression,  into  which  the  anterior  extre- 
mity of  the  urethral  canal  projects,  and  which  secretes  a 
strong-smelling  greyish  matter,  termed  smegma  preputii. 
Prom  one  infero-lateral  part  of  the  corpus  cavernosum  to 
the  other,  transverse,  dark- coloured  muscular  fibres  run 
underneath  the  urethra  and  corpus  spongiosum,  forming 
the  accelerator  urinae  muscle,  which  runs  from  the  glans 
penis  as  far  back  as  the  erectors.  Along  its  under  surface 
may  be  seen  two  bands,  apparently  of  white  fibrous  tissue, 
which  may  be  traced  as  far  as  the  lateral  part  of  sphincter 
ani.  These  are  the  retractores  penis,  composed  of  invo- 
luntary muscular  fibres. 

The  penis  as  above  described  is  inferiorly  covered  by 
skin  which  communicates  laterally  with  that  covering  the 
thighs,  superiorly  with  that  ^^ortion  extending  towards  the 
anus  over  the  sj)ace  termed  the  perineum,  and  anteriorly 
it  spreads  outwards  and  joins  the  posterior  part  of  the 
cuticular  layer  of  the  scrotum,  and  in  front  of  this  the  outer 
layer  of  the  prepuce.  The  prepuce  or  foreskin  is  a  circular 
inversion  of  the  skin  inward  to  form  mucous  membrane. 
Anteriorly  it  is  continued  forwards  to  form  a  raphe  in  the 
neighbourhood  of  the  umbilicus.  The  skin  in  this  region 
is    very  thin,  and  in  most  horses  almost   hairless.     The 


THE    ABDOMEN.  245 

mucous  membrane  lining  tlie  prej)uce  is  darkened  bj  pig- 
ment, and  presents  many  glands,  cjlandulce  odoriferce,  which 
secrete  a  peculiar  unctuous  lubricating  matter.  It  is  con- 
tinuous with  that  of  the  glans  penis.  Between  it  and  the 
skin  is  a  layer  of  yellow  elastic  tissue,  reflected  from  the 
faschia  superficialis  abdominis,  which,  forming  a  sling  be- 
neath the  anterior  part  of  the  penis,  is  termed  the  suspensory 
ligament.  From  the  central  part  of  the  under  surface  of 
symphysis  pubis  a  fibrous  ligament  extends,  composed 
of  two  diverging  portions,  one  of  which  runs  to  either 
side  of  corpus  cayernosum  ;  this  is  the  triangular  ligament 
of  the  penis,  between  its  two  parts  runs  a  vein.  This  organ 
serves  to  direct  into  the  vagina  of  the  female  the  semen  or 
tnale  fecundating  fl.uid.  Semen  is  produced  by  certain  organs, 
testes  or  testicles,  which  are  suspended  from  the  upper  part 
of  the  abdominal  cavity  in  certain  special  cavities,  vaginal 
cavities,  situated  at  the  posterior  lateral  and  inferior  part 
of  the  belly.  These  cavities  are  covered  by  layers  con- 
tinuous with  those  of  the  floor  of  the  abdomen  which  form 
the 

Scrotum,  or  "jji^r^e,"  situated  just  behind  the  sheath,  which 
presents  externally  a  layer  of  thin  skin,  along  the  central 
line  of  which  running  from  before  backwards  is  an  irregu- 
lar ridge  or  raphe.  This  covers  the  dartos  muscle,  com- 
posed of  unstriated  muscular  fibres,  continuous  with  faschia 
superficialis  abdominis,  which  throws  across  the  cavity  a 
septum  (septum  scroti),  whereby  the  right  scrotal  cavity 
is  separated  from  the  left.  It  is  contraction  of  this 
which  causes  corrugation  of  the  scrotum  under  the  in- 
fluence of  cold,  by  means  of  the  inter collumnar  faschia 
(derived  from  obliquus  abdominis  externus),  its  inner  sur- 
face is  attached  to  the  cremasteric  faschia. 

The  cremaster  muscle  is  but  a  portion  of  the  internal 
oblique  of  the  abdomen.  Arising  from  the  psoas  faschia, 
or  from  the  antero-inferior  spinous  process  of  the  ilium,  it 
passf  s  through  the  inguinal  canal  and  the  external  abdo- 
minal ring,  externally  situated  to  the  spermatic  cord,  and 
on  approaching  the  scrotum  its  fibres  form  a  species  of 
sling  serving  to  support  the  testis.  To  this  portion  the 
name  cremasteric  faschia  is  applied,  and  its  internal  surface 
is  connected  by  the  infundihuliform  faschia  (occasionally 
connected  with  transversalis  abdominis)  to  the  external 
surface  of  tunica  vaginalis  scroti  or  propria,  a  continuation 


21-6  OUTLI>ES    OF    EQUINE    ANATOMY. 

of  tlie  serous  membrane  covering  the  floor  of  tlie  belly 
through  the  inguinal  canal.  The  external  surface  of  this 
membrane  is  sroooth,  covered  with  tessellated  epithelium, 
which  secretes  a  serous  fluid  to  enable  the  surface  of  tunica 
vaginalis  testis  or  reflexa  to  glide  on  it  freely.  These  two 
serous  layers  are  posteriorly  connected  by  d^frcenimi,  which 
extends  up  as  far  as  the  loins  whence  the  testes  originally 
descended.  In  the  fcetal  colt,  as  in  adult  birds,  the  testis 
occupies  a  position  against  the  kidney.  To  its  under  part 
is  attached  a  white  fibrous  cord,  gubernaculum  testis,  sur- 
rounded by  serous  membranes,  running  to  the  internal 
abdominal  ring.  In  the  process  of  development  this  guides 
the  testis  towards  the  inguinal  canal,  and  then  becoming 
everted  in  passing  into  the  scrotum,  its  serous  covering 
becomes  the  tunica  vaginalis  scroti.  The  testis  may 
generally  be  found  in  the  scrotum  at  birth ;  it  subse- 
quently, at  a  period  varying  according  to  the  breed  and 
treatment  of  the  colt,  passes  again  into  the  inguinal  canal, 
where  it  remains  for  some  time,  sometimes  permanently, 
and  again  descends  into  the  scrotum.  Sometimes,  how- 
ever, it  is  drawn  up  into  the  abdomen,  and  on  account  of 
increase  of  its  size  is  unable  again  to  descend.  If  this 
occurs  to  but  one  testis,  the  animal  is  termed  a  monorcJiid  or 
rig,  and  if  the  other  testis  has  been  removed  by  castration, 
he  will  be  lustful,  but  an  uncertain  stock-getter. 

The  immediate  coats  of  the  testis  are  a  serous  layer, 
tunica  vaginalis  testis  and  tunica  alhuginea.  The  latter  is  a 
dense  fibrous  mass,  forming  the  stroma  of  the  organ,  send- 
ing fibres  and  septa  inwards  from  an  outer  layer,  to  support 
and  separate  the  different  lobules  of  the  gland,  and  to  in- 
vest its  larger  vessels.  It  predominates  at  the  upper  part 
of  the  organ,  where  it  is  termed  mediastinum  testis.  The 
testis  consists  of  a  number  of  long  tubules  curled  uj)on 
themselves,  forming  the  lohuli  testis.  Each  lobule  is  iso- 
lated from  its  fellows,  receives  a  vascular  coating  (by  some 
anatomists  termed  tunica  vasculosa),  and  terminates  Supe- 
riorly in  a  vas  rectum.  The  vasa  recta  unite  and  form  a 
plexus  in  the  substance  of  mediastinum  testis,  at  the 
anterior  part  of  which  they  converge  to  form  the  vasa 
effereiitia,  which  emerge  from  the  testis  proper,  and,  be- 
coming very  convoluted,  (coni  vasculosi),  form  the  j^os^mor 
globus  of  the  ejndidymis. 

The  testicle,  thus  constituted,  is  a  rounded  body,  clon- 


THE    ABDOxMEN,  247 

gated  from  before  backwards,  slightly  flattened  from  side 
to  side.  It  is  firm  to  the  touch,  but  on  laying  it  open  we 
find  that  it  consists  of  a  quantity  of  soft  greyish  matter. 
From  its  antero- superior  part  the  epididymis  commences 
and  extends  from  before  backwards,  consisting  of  an  ante- 
rior and  a  posterior  glohus^  and  a  hody.  The  anterior  ^  or 
^mailer  globus  consists  of  the  contorted  vasa  efferentia  ; 
they,  however,  unite  and  reunite,  becoming  larger  in 
calibre,  until  they  form  but  one  tube,  which,  by  its  extreme 
convolution,  forms  the  hody  and  the  ]josterior  or  major 
globus,  from  which,  as  the  vas  deferens,  it  passes  up  the 
posterior  part  of  the  spermatic  cord  towards  the  pelvis, 
where  it  becomes  dilated  on  the  superolateral  part  of  the 
bladder,  and,  after  passing  beneath  the  prostate,  opens  into 
the  urethra  near  its  commencement. 

The  epididymis  is  connected  to  the  testis  by  a  double 
fold  of  visceral  vaginal  serous  membrane,  which  is  con- 
tinued upwards  to  the  internal  abdominal  ring  surrounding 
the  spermatic  cord.  In  the  anterior  part  of  the  cord  runs 
the  extremely  convoluted  spermatic  artery  with  the  plexus 
of  spermatic  vems  or  cmyus  pamjnniforme ;  in  the  poste- 
rior part  the  vas  deferens  with  the  artery  of  the  cord.  The 
walls  of  the  sperni-bearing  vessels  or  tuhuli  seminiferi  increase 
in  complexity  from  their  commencement  to  the  termination 
of  the  vas  deferens  in  the  urethra.  At  first  they  consist  of 
but  basement  membrane  and  epithelial  cells,  in  which 
latter  may  be  seen  round  bodies,  which  in  their  course  to 
the  vas  deferens  gradually  acquire  tails,  and  at  length 
become  free  as  spermatozoa,  small,  actively  moving  bodies, 
propelled  by  the  vibration  of  an  elongated  cilium,  running 
from  the  posterior  part  of  the  cell,  giving  it  a  "  tadpole- 
like" appearance.  The  muscular  walls  of  the  vas  deferens 
^re  thick,  giving  it  its  distmctively  firm  feel  in  its  course 
through  the  spermatic  cord. 

The  testis  derives  its  nerves  from  the  hypogastric 
plexus. 

Vesiculae  seminales  are  pyriform  sacs,  resting  upon  the 
supero-posterior  part  of  the  bladder,  in  such  a  manner 
-as  to  conceal  the  terminations  of  the  ureters.  They  have 
but  very  thin  walls,  and  each  terminates  anteriorly  in  a 
blind  pouch,  posteriorly  in  the  duct  which  unites  with 
vas  deferens  to  form  the  ejaculatory  duct,  which  runs 
to  a  special    opening   on  the  veru  montanunu     It  pre- 


:2tt8  OUTLINES    OF    EQUINE    AXATOilY. 

sents  a  small  amount  of  m.uscular  structure  in  some  parts 
of  its  walls,  and  is  lined  with  mucous  membrane.  There 
is  no  doubt  but  that  it  secretes  a  special  fluid  to  be  added 
to  the  semen.  It  also  may,  to  a  certain  extent,  serve  as  a 
receptacle  for  retention  of  the  semen  until  it  is  required 
for  use. 

The  generative  organs  of  the  male  produce  the  sperm- 
cell,  those  of  the  female  the  germ-cell  or  ovum,  and  without 
contact  of  these  two  cells  reproduction  cannot  occur.  The 
ovum  is  produced  in  a  special  organ,  one  of  which  is 
situated  on  either  side  of  the  spine  in  the  lumbar  region. 
These  are  the  ovaries  or  female  testes.  They  are  smaller 
than  the  testes  of  the  male  and  more  rounded,  and  their 
external  surface  is  generally  lobulated  in  consequence  of 
projection  of  certain  vesicles  which  the  organ  contains.  It 
is  invested  by  peritoneum,  being  situated  at  the  anterior 
part  of  the  broad  ligament  of  the  uterus,  and  presents  a 
white  fibrous  stroma,  tunica  alhugmea,  embedded  in  which 
are  certain  vesicular  bodies  lined  with  tessellated  epithe- 
lium, and  containing  a  quantity  of  albuminous  fluid,  in 
which  floats  the  ovum.  These  cysts  receive  the  name 
Graafian  vesicles,  and  their  lining  membrane,  which  is 
thickest  at  that  part  with  which  the  ovum  lies  in  contact, 
is  the  memhrana  granulosa.  The  ovum  is  a  cell  consisting 
of  a  ceZ?-i6-a?/,  zona  pelliicida,  and  cell  contents;  the  latter 
consists  of  a  nucleus  or  germinal  vesicle,  and  a  nucleolus 
or  germinal  spot,  floating  in  an  albuminous  fluid. 

The  Graafian  vesicles  are  sraallest  at  the  centre  of  the 
organ,  and  gradually  increase  in  size  on  extending  towards 
the  outer  surface.  By  pressure  they  cause  absorption  of 
the  stroma,  and  thus  at  length  bulge  against  the  peritoneal 
coat  of  the  organ.  Finally  they  rupture,  thus  discharging 
their  contents  into  the  Fallopian  tube.  This  occurs  when 
the  animal  is  in  "heat,"  as  it  is  commonly  termed,  and 
thus  the  ova  commence  their  process  of  development  into 
the  foetus.  After  rupture  the  Graafian  vesicles  become 
filled  with  a  mixture  of  blood  and  lymph,  Vv'hich  undergoes 
contraction  and  organization  until  a  stellate  cicatrix,  corpus 
luteum,  is  produced,  which  is  much  more  persistent  when 
its  ovum  has  been  impregnated  than  when  it  has  under- 
gone no  further  stage  of  development.  These  bodies 
form  our  main  guide  in  post-mortem  decision,  as  to 
whether    an    animal    has    ever    been    pregnant   or  not. 


THE   ABDOMEN.  249 

Attached  to  the  ovary  is  the  Fallopian  tube,  a  trumpet- 
shaped  organ,  the  anterior  extremity  of  which  presents  a 
very  irregular  margin,  which  is  much  jagged,  and  is 
termed  the  jimhriated  extremity  or  morsus  diaholi.  It  is  one 
of  the  divisions  of  this  extremity  which  connects  it  to  the 
ovary.  It  is  perforated  by  a  canal,  which  posteriorly  gains 
the-  cavity  of  the  uterus  at  a  very  small  extremity  in  the 
extreme  anterior  part  of  the  horn  of  that  organ.  Ante- 
riorly it  dilates,  opening  into  a  peculiar  serous  sac  of  which 
the  ovary  forms  one  boundary  and  which  communicates  on 
one  side  freely  with  the  main  peritoneal  cavity.  The 
ciliated  epithelium  with  which  it  is  lined  is  here  replaced  by 
tessellated  epithelium.  This  is  considered  remarkable  as  an 
instance  of  a  mucous  membrane  being  directly  continuous 
with  a  serous  membrane,  but  the  histological  distinction 
between  the  two  is  insignificant.  During  sexual  excite- 
ment the  fimbriated  extremity  is  supposed  to  grasp  the 
ovary,  approximating  its  anterior  opening  to  the  rupturing 
Graafian  vesicle.  The  tubes  are  convoluted,  and  present 
muscular  fibres  of  the  unstriated  class  in  their  walls. 

The  uterus  is  a  large  organ  which  occupies  the  anterior 
part  of  the  pelvis  and  the  posterior  part  of  the  abdomen. 
Its  position,  however,  varies  with  its  j^regnant  or  unim- 
pregnated  condition.  Anteriorly  it  is  bifid,  presenting 
two  rounded  sacs,  the  cornua  or  liorns.  These  meet  at 
an  acute  angle  in  the  mare ;  thus  the  equine  uterus  pre- 
sents no  fundus  or  space  between  the  cornua.  They  open 
into  the  body,  which  extends  backwards  to  terminate  in- 
the  nech,  the  portion  running  for  a  short  distance  into  the 
vagina  to  terminate  at  the  os  uterinum  externum.  The 
oj^ening  leading  from  the  cavity  of  the  body  of  the  organ 
to  the  passage  of  the  neck  is  os  uterinum  internum.  The 
uterus  is  completely  enveloped  by  peritoneum,  being  en- 
closed in  a  double  fold  of  that  membrane,  which  on  either 
side  extends  to  the  supero -lateral  parts  of  the  abdomen, 
forming  the  hroad  ligaments  of  the  uterus,  on  the  free  mar- 
gin of  which  are  the  ovary,  fallopian  tube,  and  uterine 
horn.  Between  the  two  layers  of  this  ligament  the  round 
ligament  of  the  ovary  runs  from  that  organ  to  the  extre- 
mity of  the  horn  of  the  uterus,  from  which  point  another 
white  fibrous  (or  muscular  band)  runs  towards  the  internal 
abdominal  ring,  where  it  becomes  lost,  the  round  liga- 
ment of  the   uterus.     The  ovarian  artery,  after  bemg 


250  OUTLINES    OF    EQUINE    ANATOMY. 

given  off  by  the  posterior  aorta,  runs  tlirougli  tlie  broad 
ligament  to  the  ovary,  wliere  it  breaks  up,  forming,  accord- 
ing to  some  anatomists,  a  tunica  vasculosa  surrounding  the 
organ.  It  corresponds  to  the  spermatic  artery  of  the  male, 
than  which  it  is  much  smaller.  Through  this  ligament, 
the  vessel  corresponding  to  the  artery  of  the  cord  in  the 
male,  the  uterine  artery  takes  a  convoluted  course  down- 
wards and  backwards.  It  is  much  larger  than  the  artery 
of  the  cord,  and  increases  very  considerably  in  size  during 
pregnancy.  The  muscular  coat  of  the  uterus  presents  two 
layers  of  fibres  ;  longitudinal  externally,  circular  internally 
(it  also  has  oblique  fibres) .  These  are  of  the  unstriated  order, 
but  during  pregnancy  become  developed  into  fibres  with  faint 
traces  of  striae.  The  mucous  membrane  is  of  a  reddish  colour, 
and  collected  into  rugae  in  the  unimpregnated  uterus.  It 
becomes  highly  vascular,  and  its  epithelium  much  increased 
in  quantity  during  pregnancy  ;  for  the  blood  of  the  foetus 
passes  to  the  chorion,  a  membrane  lying  in  intimate  con- 
tact with  the  vascular  part  of  the  mucous  membrane  of 
the  dam,  and  in  which  the  ^^rocess  of  aeration  of  the  blood 
ensues.  (The  excess  of  epithelium  after  parturition  is 
thrown  off  as  the  membrana  decidua.)  In  some  parts, 
especially  up  against  the  fallopian  tubes,  the  epithelium 
is  ciliated,  serving  to  waft  the  spermatozooa  upwards. 
Around  the  neck  of  the  organ  the  mucous  glands  increase 
in  complexity,  and  secrete  a  more  viscid  matter ;  they  are 
the  glandulce  of  Nahoth.  The  muscular  coat  in  the  cervix 
uteri  is  very  thick,  thereby  causing  puckering  of  the 
mucous  membrane  longitudinally  in  this  part ;  laterally 
it  comes  in  contact  with  the  muscular  coat  of  the  vagina, 
and  posteriorly,  covered  by  the  mucous  membrane,  pro- 
jects in  a  remarkable  manner  into  the  vaginal  cavity  "like 
the  tap  of  a  beer  barrel,"  thus  forming  the  cauliflower 
excrescence  {fleur  ^panouie  of  the  French  anatomists) ,  which 
projects  more  inferiorly  than  superiorly. 

The  vagina  is  the  cavity  placed  immediately  posterior 
to  the  uterus  extending  to  the  vulva,  from  which  it  is 
separated  by  the  hymen.  It  is  largest  centrally,  becoming 
anteriorly  constricted  in  surrounding  os  uteri,  and  running 
to  join  the  cervix  ;  posteriorly  smaller  in  joining  the  vulva  ; 
superiorly  it  is  in  contact  with  the  rectum  ;  inferiorly  with 
the  bladder.  Its  anterior  part  is  covered  with  peritoneum, 
which  laterallv  blends  with  the  broad  ligaments  of  the 


THE    ABDOMEN.  251 

uterus,  and  sends  off  longitudinal  folds;  superiorly  the 
vagino -rectal,  inferiorly  the  vagino-vesical,  folds  to  tlie 
rectum  and  bladder  respectively.  It  presents  also  a  mus- 
cular coat  with  longitudinal  and  circular  fibres  ;  in  contact 
with  this  lies  a  quantity  of  erectile  tissue,  analogous  to  that 
forming  the  corpus  spongiosum  of  the  penis.  It  is  lined 
by'  mucous  membrane,  with  stratified  squamous  epithe- 
lium, and  which  anteriorly  becomes  puckered  up  to  join 
that  of  the  nect  of  the  uterus  ;  posteriorly  forms  a  re- 
markable double  fold,  hymen,  almost,  but  seldom  com- 
pletely, separating  the  vaginal  cavity  from  that  of  the 
vulva.  Generally  lunate  in  the  virgin,  it  is  lacerated  in 
the  first  act  of  coition  by  the  penis  of  the  stallion,  and 
subsequently  appears  as  an  irregular  fringe  extending 
round  the  vagino-vulval  opening,  carunculsB  myrtiformes. 

The  vulva  leads  from  the  vagina  to  the  external  genera- 
tive opening,  and  presents  coats  similar  to  those  of  the 
vagina,  with  a  much  greater  quantity  of  erectile  tissue 
(bulb  of  vulva).  Posteriorly  the  muscular  coat  becomes 
redder  in  colour,  with  its  fibres  striated  and  arranged  in 
a  circular  manner  around  the  external  opening,  forming 
the  sphincter  vaginsB  (more  correctly  sphincter  vulvse). 
The  floor  of  the  vulva,  just  behind  the  hymen,  about  four 
inches  from  the  lower  j)art  of  the  external  opening,  pre- 
sents the  meatus  urinarius  externus,  much  larger  than 
that  of  the  male,  being  the  opening  from  a  larger  canal ; 
between  this  and  the  hymen  anteriorly  is  a  valvular  flap 
of  mucous  membrane. 

The  external  generative  opening  is  an  elliptical  fissure 
extending  from  above  downwards.  It  terminates  above  in 
an  acute  angle,  superior  commissure,  situated  about  two 
inches  below  the  anus,  the  intermediate  space  being  peri- 
neum. Below,  it  is  more  rounded,  forming  the  inferior 
commissure.  The  opening  is  bounded  laterally  by  the 
labia,  elongated  prominences  consisting  of  the  sphincter 
vulvae,  fat,  and  vascular  structure  covered  externally  by 
thin,  hairless  skin,  which  externally  is  continuous  with  the 
mucous  membrane  of  the  vulva,  the  latter  becoming  folded 
longitudinally  to  form  the  labia  minora  or  nymphse.  At 
the  inferior  commissure  is  a  triangular  space,  which  may 
be  exposed  by  sej^aration  of  the  labia,  fossa  navicularis, 
on  which  projects  the  clitoris,  a  small  organ  analogous  to 
the  penis  of  the  male,  and  the  seat  of  the  pleasure  expe- 


252  OUTLINES    OF   EQUINE   ANATOMI. 

rienced  during  sexual  intercourse.  It  is  surrounded  "by 
a  mucous  fold,  prseputiiim  clitoridis,  whicli  covers  its  free 
extremity,  and  centrally  presents  a  depression  leading  into 
a  blind  sac,  wliicli  generally  contains  an  odorous  oily 
matter.  This  organ  is  fixed  by  two  crura  to  the  ischial 
arch,  has  two  erectores  clitoridis  running  to  its  substance 
from  the  same  part,  a,nd  presents  a  corpus  cavernosum,  a 
corpus  spongiosum,  and  a  cjlans. 

The  young  animal  at  birth  being  incapable  of  supplying 
itself  with  nutriment,  and  even  incapable  of  digesting  or- 
dinary alimentary  matters,  is  for  a  time  supplied  with 
milk  produced  by  the  mammary  gland  of  the  dam.  This 
function  the  mare  shares  in  common  xvWh  all  the  females 
of  the  higher  order  of  vertebrated  animals,  mammalia. 
Situated  between  the  thighs  are  two  prominences,  from  the 
under  part  of  which  small  finger-like  portions  project, 
having  at  their  extremity  three  or  four  small  openings. 
These  are  the  teats,  and  they  are  covered  by  a  continuation 
of  the  delicate  skin  investing  the  mammary  glands.  They 
are  longest  in  the  animal  which  has  "  given  suck."  The 
faschia  superficialis  abdominis,  at  the  postero-inferior  part 
of  the  abdomen  of  the  mare,  is  reflected  downwards  to 
invest  the  mammary  gland.  It  sends  in  septa  between 
the  different  lobes,  for  this  is  a  racemose  gland,  presenting 
a  structure  similar  to  that  of  the  salivary  glands.  Its 
primary  secreting  saccules,  lined  by  spheroidal  epithelium, 
open  mto  the  primary  ducts,  which  unite  and  reunite  with 
those  from  other  j^arts  of  the  gland,  until  at  length  they 
terminate  in  a  dilated  cavity  at  the  base  of  the  teat,  galac- 
tophorous  sinus.  This  is  divided  into  parts  corresponding 
in  number,  and  leading  by  ducts  to  the  openings  on  the 
teats.  The  teats  contain  yellow  elastic  tissue,  but  no  mus- 
cular fibre,  for  the  milk  is  withdrawn  by  the  suction  action  of 
the  young  animal.  Around  the  openings  the  skin  becomes 
continuous  with  the  mucous  membrane  of  the  glands. 

Milk  consists  of  water  with  an  albumenoid  matter, 
casein  (cheese),  and  salts,  in  solution.  Floating  in  it  are 
numerous  fat- globules,  which  form  the  cream.  The  first  milk 
produced  after  foaling  contains  a  number  of  the  epithelial 
cells  of  the  gland  in  a  state  of  fatty  change,  a  number 
of  fat-globules  being  connected  together  by  the  tough 
w^all  of  the  cell,  forming  the  peculiar  colostrum-corpuscles, 
for  this  milk  is  termed  colostrum  (or  beastlings).    It  has  a 


THE    ABDOMEN.  253 

laxative  effect,  and  serves  to  remove  from  tlie  alimentary 
canal  of  the  newly  born  animal  the  meconium  or  inspissated 
biliary  matter  which  has  accumulated  in  the  intestines 
while  the  animal  was  in  the  uterus,  in  consequence  of  the 
large  supply  of  blood  received  by  the  liver  during  that 
period.  Where  this  precaution  is  neglected,  the  meconium 
sometimes  collects  in  large  quantities  of  pellets,  like  sheep 
dung  in  the  rectum,  causing  obstinate  constipation. 

The  dissector  may  be  fortunate  enough  to  obtain  a  preg- 
^nant  animal  for  dissection  ;  he  will  then  be  enabled  to 
study  the  FCETAL  APPENDAGES.  By  cutting  through 
the  walls  of  the  uterus,  he  will  expose  the  chorion  lying 
in  immediate  contact  with  the  uterine  mucous  membrane 
over  its  whole  surface.  It  consists  of  an  intricate  network 
of  blood-vessels  arranged  in  a  ^^lexiform  manner  to  come 
in  apposition  with  the  vascular  layer  of  the  uterine  mucous 
membrane.  While  in  these  vessels,  being  separated  from 
the  blood  of  the  dam  only  by  layers  of  epithelial  cells  and 
of  basement  membrane,  the  blood  of  the  foetus  is  enabled 
to  exchange  carbonic  anhydride  for  oxygen,  sufficient  in 
quantity  to  support  his  torpid  life,  for  he  moves  but  little, 
and  his  temperature  is  maintained  by  that  of  his  dam  in 
whose  body  he  lies ;  thus  two  of  the  demands  for  oxygen 
in  the  blood  which  obtain  after  birth  are  absent  in  the 
foetus,  and  his  life  consists  more  in  active  addition  to 
existing  structures,  growth,  than  in  disintegration  of  tissue 
with  substitution  of  fresh  matter,  such  as  obtains  in  the 
adult.  Blood  from  the  internal  iliac  branch  of  the  posterior 
aorta  of  the  foetus  passes  through  the  umbilical  arteries. 
These  vessels,  which  in  the  adult  become  impervious,  de- 
generating into  the  round  ligaments  of  the  Madder,  after 
becoming  attached  to  their  respective  sides  of  the  bladder 
gain  the  umbilical  opening  ;  here  they  unite  and  form  one 
vessel,  which  runs  outside  the  body  of  the  foetus  to  the 
chorion  through  the  umbilical  cord.  The  veins  of  the 
chorion  unite  and  reunite  to  at  last  form  two  vessels  which 
pass  along  the  umbilical  cord,  and  on  gaining  the  umbili- 
cus unite  to  form  the  umbilical  vein,  which  runs  in  a- 
forward  direction  along  the  floor  of  the  belly  between  the 
peritoneal  folds, forming  the  falciform  ligament  of  the  liver 
to  which  organ  it  runs  without  (in  the  colt)  having  any  direct 
communication  with  the  posterior  vena  cava  through  the 
ductus  venosus  as  found  in  many  other  animals.     It  passes 


254  OUTLINES    OP    EQUINE    ANxiTOMY. 

between  two  of  tlie  divisions  of  lobulus  scissatus,  where  it 
breaks  np,  and  its  blood,  after  ramifying  througli  the  liver 
(which  is  very  large  in  the  foetus),  as  in  the  adult,  gains 
the  posterior  vena  cava  through  the  hepatic  veins.  It 
thus  passes  to  the  heart,  and  the  major  portion  of  it 
through  the  foramen  ovale  in  the  septum  auricularum 
into  the  left  auricle,  where  it  meets  with  blood  from  the 
lungs,  and  with  it  through  the  left  ventricle  passes  into  the 
aorta,  and  from  that  into  the  anterior  aorta,  for  the  pos- 
terior aorta  is  mainly  occupied  by  another  current.  The 
blood  which  gained  the  right  auricle  from  the  anterior  vena 
cava,  though  a  small  amount  of  it  passes  through  foramen 
ovale,  for  the  most  part  having  traversed  the  right  ven- 
tricle, gains  the  pulmonary  artery,  from  which  some  passes 
to  the  lungs,  but  a  considerable  portion  through  the  ductus 
arteriosus,  a  vessel  connecting  the  pulmonary  artery  to  the 
posterior  aorta.  Through  the  posterior  aorta  some  passes 
to  the  body  of  the  foetus  and  some  through  the  uterine 
arteries  to  be  reoxygenated  in  the  chorion.  Foramen  ovale 
is  an  opening  through  septum  auricularum  just  in  front  of 
the  termination  of  the  posterior  vena  cava ;  it  is  guarded 
by  a  valve  formed  of  a  double  fold  of  endocardium.  After 
birth  it  becomes  obliterated  on  the  left  side,  traces  of  it 
remaining  on  the  right  side,  forming  the  fossa  ovalis  sur- 
rounded by  a  prominent  yellow  ring,  annulus  ovalis. 

Immediately,  but  loosely,  surrounding  the  foetus  in  utero 
is  the  amnion.  This  is  a  thin  membrane  which  presents 
some  extremely  convoluted  vessels,  ramifying  over  its 
surface,  and  serves  to  secrete  a  fluid  in  which  the  foetus 
floats  (liq[UOr  aninii) .  It  is  contmuous  with  the  skin  of 
the  foetus  at  the  umbilicus,  becoming  reflected  over  that 
portion  of  the  umbilical  cord  nearest  to  this  opening,  and 
which  is  therefore  termed  the  amniotic  portion.  Floating 
about  in  the  liquor  amnii  generally  are  one  or  more 
brownish  masses  of  soft  substance.  These  are  the  hippo - 
manes,  and  are  supposed  to  be  composed  of  nutritious 
matter.  Sometimes  they  are  attached  to  the  inner  sur- 
face of  the  amnion.  In  this  country  they  are  generally 
termed  ''false  tongues,''  from  their  peculiar  shape. 

Investing  the  amnion,  and  lining  the  chorion,  is  a  serous 
membrane,  the  allantois.  Its  parietal  or  cJiorial  fortiori  is 
continuous  with  its  visceral  or  amniotic  portion  by  a  portion 
reflected  over  that  part  of  the  umbilical  cord  which  ex- 


THE    ABDOJIEN.  255 

tends  from  tlie  amnion  to  tlie  chorion.  The  amnion 
presents  the  characters  of  all  other  serous  membranes,  but 
it  contains  the  urine  of  tke  foetus,  since  the  allantoid  sac 
is  brought  into  communication  with  the  bladder  of  the 
foetus  (from  which  it  was  originally  derived)  by  the 
urachus,  a  tube  running  through  the  amniotic  part  of  the 
umbilical  cord.  The  foetus  in  utero,  therefore,  is  surrounded 
by  his  own  urine.  The  umbilical  cord,  therefore,  is 
divided  into  two  parts  :  The  allantoid portio7i  consists  simply 
of  two  umbilical  veins,  and  an  umbilical  artery  surrounded 
by  the  allantois.  The  amniotic  portion,  in  addition,  contains 
the  urachus,  and  those  vessels  which  belong  to  the  amnion. 
In  both  parts  the  vessels  receive  coatings  of  embryonic  cells^ 
and  in  the  amniotic  portion  the  vessels  are  arranged  spirally, 
giving  this  part  a  rope-like  appearance.  Finally,  we 
may  notice  that  the  bladder  of  the  foetus  is  larger  in  propor- 
tion than  that  of  the  adult,  extending  to  the  umbilicus,  where 
it  terminates  in  the  urachus.  That  the  so-called  vascular 
glands  are  largest  in  the  foetus  (in  proportion)  ;  that  the 
kidneys  are  lobulated;  the  testes  in  the  lumbar  region  in  the 
colt ;  and  the  lungs,  dark  red  solid  organs,  for  they  have 
not  yet  been  filled  with  air.  When  the  labour-pains  of 
the  dam  occur  the  chorion  is  ruptured,  and  the  amnion 
with  its  serous  layer  is  the  first  to  protrude  through  the 
external  opening,  being  vulgarly  termed  the  "  water  bag  J' 
On  rupture  of  this  the  foetus  is  expelled,  and  sometimes  in 
falling  ruptures  the  umbilical  cord.  The  membranes 
follow  at  variable  periods.  On  first  feeling  the  chill  ex- 
ternal air  the  young  animal  gasps,  and  so  draws  air 
through  the  trachea,  it  permeates  the  air-vessels,  and  for 
the  rest  of  his  life  the  animal  is  an  air-breather.  Those 
communications  between  the  several  portions  of  the  vascular 
arrangement  of  the  foetus,  which  are  not  required  after 
birth  speedily  become  impervious  ;  if  they  are  persistent 
they  cause  disease. 

We  may  examine  the  attachments  of  some  muscles 
underneath  the  loins. 

Psoas  magnus  arises  as  far  forward  as  the  inner  surface 
of  the  last  two  ribs;  it  is  attached  to  the  transverse 
processes  of  the  lumbar  vertebrae,  and  its  fibres  interiorly 
join  with  iliacus  in  becoming  inserted  into  trochanter  minor 
internus.  Arteria  profunda  femoris  runs  across  the  in- 
ferior tendon. 


256  OUTLINES    OP    EQUi>,'E    ANATOMY. 

Psoas  parvus  is  longer  and  thinner  tlian  psoas  magnns. 
Its  fibres  from  the  lateral  part  of  the  bodies  of  the  last 
three  dorsal  and  the  anterior  liJinbar  vertebrae  converge 
to  form  a  tendon,  which  becomes  inserted  into  the  brim  of 
the  pelvis  midway  between  the  antero -inferior  spinous 
process  of  the  ilium  and  the  acetabulum. 

Quadratus  lumborum  is  attached  to  the  last  rib,  and  to 
the  transverse  process  of  all  the  lumbar  vertebrae  running 
to  the  venter  ilii  near  the  crista. 

Intertransversales  lumborum  are  situated  between  the 
transverse  processes  of  the  lumbar  vertebraa. 

The  psoas  faschia  covers  the  under  surface  of  the  psose 
muscles.  It  affords  attachment  to  transversalis  abdominis 
and  obliquus  abdominis  internus,  and  from  it  in  some  sub' 
jects  arise  sartorius  and  cremaster  muscle. 


THE    HIND    EXTIIE5IITY.  257 


PART    IX.— SPECIAL   ANATOMY. 
The  Hind  Extremity. 

From  an  incision  wliicli  the  operator  fii'st  makes  along 
the  central  line  of  the  quarters  he  dissects  the  skin  back 
over  the  external  surface  of  the  quarter,  and  posteriorly  as 
far  as  the  incision  originally  made  along  the  central  and 
inferior  line  of  the  body  towards  the  root  of  the  tail. 
By  so  doing  he  exposes  a  wide-sj^read  and  rather  thick 
layer  of  substance  of  an  elastic  fibro-adipose  material, 
which  covers  the  muscles  of  the  quarter,  and  anteriorly 
blends  with  the  lumbar  faschia,  while  superiorly,  in  blend- 
ing with  its  corresponding  layer  from  the  opposite  side,  it 
becomes  firmly  attached  to  the  superior  vertebral  ligament 
in  the  sacral  region.  This  faschia  of  the  quarter  inferiorly 
is  imperceptibly  blended  with  the  faschia  lata  or  the  faschia 
covering  the  thigh,  and  on  removing  it  we  find  that  gluteus 
maximus  and  gluteus  externus  are  attached  to  it  to  a  con- 
siderable extent,  whence  care  is  required  in  the  process 
to  avoid  injuring  the  appearance  of  the  subject.  By  its 
removal  we  expose  the 

Gluteus  externus,  a  Y-shaped  muscle,  that  is  to  say, 
one  with  two  points  of  origin,  which  converge  to  a  common 
centre  of  insertion.  The  anterior  part  we  shall  find  arises 
in  common  with  tensor  vaginae  femoris  from  the  inferior 
part  of  the  antero -inferior  spinous  process  of  the  ilium, 
while  the  posterior  is  attached  to  the  spines  and  transverse 
processes  of  the  second  and  third  sacral  bones.  The  mus- 
cular fibres  of  both  these  parts  are  more  or  less  attached  to 
the  under  surface  of  the  gluteal  faschia,  and  blend  opposite 
the  anterior  tubercle  of  trochanter  major,  where  they  be- 
come, for  the  most  part,  tendinous,  and  from  this  they  run 
to  the  trochanter  minor  externus,  where  they  are  firmly 
inserted.    Over  the  anterior  tubercle  this  tendon  plays  freely 

17 


258  OUTLINES    OF    EQUINE    ANATOMY. 

through  the  medium  of  a  synovial  bursa.  Almost  as  far 
as  the  inferior  part  of  the  anterior  extremity  of  this  muscle 

Tensor  vaginae  femoris  blends  with  its  anterior  part  to 
a  considerable  extent.  It  arises  from  the  inferior  part  of 
the  antero-inferior  spinous  process  of  the  ilium,  and  in- 
feriorly  forms  an  aponeurotic  expansion,  which  blends  with 
the  faschia  lata,  and  which  slightly  extends  over  the  in- 
ternal surface  of  the  muscles  in  front  of  the  femur.  It 
becomes  firmly  attached  to  the  external  surface  of  the  pa- 
tella. By  dividing  and  dissecting  back  these  muscles  we 
expose 

Gluteus  maximus,  a  large  bulky  mass  of  muscular  sub- 
stance, clothing  the  dorsum  of  the  ilium.  It  arises  from 
the  tendinous  structure  of  the  longissimus  dorsi  by  a  pro-- 
jecting  process,  which  grows  narrower  and  thinner  until  it 
terminates  opposite  the  last  rib ;  from  the  antero-inferior 
and  supero-posterior  spinous  processes  and  dorsum  surface 
of  the  ilium  as  far  down  as  the  neck  ;  also  from  the  ante- 
rior part  of  the  sacro-sciatic  ligament.  Inferiorly  it  is  in- 
serted by  two  heads;  one  runs  to  the  anterior  tubercle  of 
trochanter  major  of  the  femur,  it  constitutes  a  broad 
tendon,  which  first  passes  over  the  superior  smooth  surface, 
from  which  it  is  separated  by  a  bursa,  and  then  becomes 
attached  to  a  roughened  ridge  ;  the  other  contains  mus- 
cular fibres,  and  after  becoming-  inserted  into  the  prominent 
posterior  tubercle  of  this  eminence,  sends  muscular  fibres 
to  the  ridge  running  from  it  to  trochanter  minor  externus. 
By  careful  division  of  this  muscle  inferiorly  we  may  expose 
gluteus  internus,  which  arises  from  the  external  surface  of 
the  neck  of  the  ilium,  and  runs  to  the  roughened  internal 
surface  of  trochanter  major ;  it  crosses,  and  is  attached  to 
the  capsular  ligament  of  the  hip-joint,  and  on  the  dry 
bones  its  superior  point  of  attachment  is  marked  by  a 
transverse  irregular  ridge. 

Triceps  abductor  femoris  arises  from  the  superior 
spinous  ligament  of  the  middle  sacral  bones,  and  from  the 
sheath  of  faschia  which  invests  the  coccygeal  muscles  of 
the  lateral  part  of  the  sacrum,  blending  with  biceps  ro- 
tator tibialis,  from  the  sacral  transverse  process,  and  from 
the  sacro-sciatic  ligament ;  it  receives  a  bulky  mass  from 
the  tuberosity  of  the  ischium,  and  after  sending  a  some- 
what irregular  fibrous  band  to  the  posterior  surface  of  the 
femur,  midway  between  the  two  small  trochanters  (with 


THE    HIND    EXTREMITY.  259 

ischio-femoralis),  divides  into  three  portions.  The  siqw- 
rior  runs  to  the  outer  surface  of  the  patella,  the  middle  to 
the  outer  surface  of  the  tibia  and  the  outer  straight  liga- 
ment of  the  patella,  blending  with  the  faschia  lata,  the 
■inferior  is  said  to  blend  with  gastrocnemius  externus,  biit 
careful  examination  shows  that  it  joins  the  white  fibrous 
tissue  layer,  which  arises  from  a  ridge  in  common  with 
that  muscle,  and  with  this  runs  to  form  that  firm  tendinous 
band  into  which  plantaris  passes,  and  which  extends  to  the 
point  of  the  hock. 

Biceps  rotator  tibialis  arises  from  the  superspinous  liga- 
ment and  the  transverse  process  at  the  posterior  part  of  the 
sacrum,  like  the  other  muscles  of  the  region,  somewhat  in- 
definitely. It  forms  a  considerable  portion  of  the  fleshy  mass 
of  the  quarter,  and  in  its  course  down  the  limb  receives  a 
branch  of  equal  size  from  the  tuberosity  of  the  ischium. 
Through  thus  reinforced,  it  forms  a  somewhat  small  tendon, 
wliich  winds  round  the  smooth  internal  surface  of  the  tibia, 
where  it  is  lubricated  by  synovia  to  reach  the  sharp  ridge 
on  the  antero-superior  part  of  that  bone.  From  this  tendon 
also  a  white  fibrous  band  runs  to  the  hock.  This  muscle  is 
also  termed  semi-tendinosus.  Posteriorly  it  is  in  contact 
with  semi-memhranosus  or 

IscMo -tibialis,  the  muscle  which  forms  the  prominence 
at  the  posterior  part  of  the  quarter.  This  muscle  arises 
mainly  from  the  tuberosity  of  the  ischium,  but  superiorly 
sends  a  thin  band  in  an  upward  direction  to  be  attached  to 
the  sacro-ischiatic  ligament  and  to  the  posterior  sacral  and 
the  anterior  coccygeal  bones.  Inferiorly  it  passes  to  the 
internal  surface  of  the  inferior  extremity  of  the  femur 
and  of  the  head  of  the  tibia,  and  the  lateral  ligament  which 
connects  them.  It  also  sends  a  band  of  white  fibrou-^ 
tissue  to  unite  with  that  of  biceps  rotator  tibialis  and 
run  to  the  point  of  the  hock.  By  removal  of  the  three 
last-mentioned  muscles  we  expose  superiorly,  up  at  the 
lateral  part  of  the  spine,  the  coccygeal  muscles  enveloped 
in  a  white  fibrous  tissue  sheath.  Below  this  the  sacro- 
sciatic  and  the  sacro-ischiatic  ligaments,  on  the  external 
surface  of  which  are  to  be  seen  the  gluteal  and  sacro- 
sciatic  nerves,  and  the  gluteal  arterial  branches  which 
emerge  from  the  jDelvis  through  foramina  in  the  liga- 
ment. At  the  infero-posterior  part  we  see  certain  muscles 
winding  round  the  neck  of  the  ischium  to  become  inserted 


260  OUTLINES   OF   EQUINE    ANATOMY. 

into  the  troclianteric  fossa.  Having  examined  tliese 
muscles  on  the  outer  surface  of  the  limb,  we  will  now  ex- 
amine those  which  form  the  rounded  fleshy  mass  on  the 
inside  of  the  thighs.  On  removal  of  the  skin  from  the 
central  line  we  expose  gracilis,  occupying  the  posterior 
part  of  this  region,  sartorius  centrally,  vastus  internus  an- 
teriorly placed.  Between  gracilis  and  sartorius  pass  a 
large  branch  of  the  crural  nerve  and  the  vena  saphena,  to 
gain  the  femoral  space.  They  run  from  the  hock  over  the 
inner  surface  of  the  tibia  and  the  thigh  immediately 
beneath  the  skin. 

Gracilis,  supero-posteriorly,  intercrosses  its  tendinous 
fibres  with  those  of  its  fellow,  and  supero- anteriorly  blends 
with  the  .tendon  common  to  the  abdominal  muscles  ;  it  is 
thus  indirectly  attached  superiorly  along  the  whole  length 
of  the  pelvic  symphysis.  We  have  to  cut  through  the  ten- 
dinous structures  at  the  point  of  junction  of  the  two  limbs 
for  more  than  an  inch  before  we  reach  the  bone.  Inf eriorly 
this  muscle  forms  an  expanded  tendon,  which  sends  off  a 
band  passing  to  the  white  fibrous  tissue  band  running 
to  the  hock,  but  mainly  becomes  inserted  into  the  inner 
straight  ligament  of  the  patella,  into  the  inner  part  of  the 
head  of  the  tibia,  and  into  the  faschia  clothing  the  inside 
of  the  thigh,  blending  anteriorly  with 

Sartorius,  a  thin  long  ribbon-like  muscle,  which  arises 
from  the  under  surface  of  the  psoas  faschia,  and  from  the 
antero -inferior  spinous  process  of  the  ilium  through  the 
medium  of  iliacus,  and  is  inserted  by  blending  inferiorly 
with  gracilis.  It  covers  that  portion  of  the  crural  nerve 
which  intervenes  between  the  brim  of  the  pelvis  and  the 
femoral  space. 

The  femoral  space  is  an  elongated  space  situated  in  this 
region,  through  which  pass  the  femoral  artery  and  vein, 
and  crural  nerve ;  and  which  also  contains  the  inguinal 
lymphatic  glands  and  some  fat.  It  is  bounded  :  anteriorly, 
by  sartorius  ;  posteriorly,  by  pectineus,  and  biceps  adductor 
f emoris  inferiorly  ;  externally  by  vastus  internus ;  inter- 
nally, by  gracilis. 

On  removing  the  layer  of  muscles  formed  by  gracilis 
and  sartorius  we  expose  supero-anteriorly  vastus  internus 
and  rectus  femoris  ;  posteriorly  ischio-tibialis  and  biceps 
rotator  tibialis ;  centrally  pectineus  and  biceps  adductor 
femoris,  between  which  run  an  artery,  vein,  and  nerve. 


THE    HIND    EXTREMITY.  261 

A  thick  band  of  white  fibrous  tissue  fills  up  the  trian- 
gular space,  which  is  bounded  by  the  brim  of  the  pelvis  on 
either  side  from  the  pectineau  tubercle  to  the  symphysis. 
Around  this  the  pectineiis  winds  in  a  direction  backwards 
to  its  insertion  into  a  roughened  line  on  the  inner  surface 
of  the  femur,  commencing  at  the  inferior  extremity  of  the 
trochanter  minor  internus.  To  the  under  surface  of  the 
above-mentioned  ligament  is  attached  the  common  tendon 
of  the  abdominal  muscles,  and  from  each  of  its  lateral 
parts  a  round  tendinous  cord  runs  to  pass  above  the  trans- 
verse ligament  of  the  hip- joint,  and  becomes  inserted  into 
the  head  of  the  femur ;  it  is  the  puhio-femoral  ligament. 
Posteriorly  placed  to  this  is  a  large  vein  which  runs  from 
one  external  iliac  vein  in  a  transverse  direction  to  the  other, 
and  which  receives  on  either  side  in  the  male  a  branch  from 
the  penis,  in  the  female  from  the  mammary  gland ;  by 
this  vein  (the  transverse  branch)  pectineus  is  separated 
from  the  small  head  of 

Biceps  adductor  femoris,  which  arises  from  the  under 
surface  of  symphysis  pubis.  The  large  head  of  this  muscle 
arises  from  the  under  surface  of  symphysis  ischii ;  opposite 
trochanter  minor  internus,  the  two  combine  to  form 
a  single  fleshy  mass,  the  muscle  then  rediyides ;  the 
smoiler  head  becomes  inserted  into  the  posterior  part 
of  the  middle  and  inferior  thirds  of  the  femur  just 
below  the  inner  small  trochanter ;  the  large  extends 
obliquely  over  the  posterior  surface  of  the  femur  as  far 
down  as  the  outer  condyle  ;  the  femoral  artery  and  vein 
pass  between  its  fibres,  thus  apparently  dividing  it  into 
two  heads,  the  lower  of  which  blends  with  the  inser- 
tion of  ischio-tibialis,  thus  becoming  attached  to  "  the  in- 
ternal surface  of  the  inferior  extremity  of  the  femur,  and 
of  the  head  of  the  tibia  and  the  lateral  ligament  which 
connects  them." 

On  removal  of  these  muscles  we  expose  the  insertion 
common  to  iliacus  and  psoas  magnus  into  trochanter  minor 
internus. 

Iliacus  arises  from  the  venter  surface  of  the  ilium,  ex- 
tending as  far  downwards  as  the  pectineau  tubercle,  as  far 
back  as  the  transverse  process  of  the  first  sacral  bone  to 
which  it  is  attached.  It  is  in  contact  v/ith  the  inner  surface 
of  the  capsular  ligament  of  the  hip-joint,  to  which  it  is 
attached,  and  blends   with  psoas  magnus   to  become  in- 


262  OUTLINES    OF    EQUINE    ANATOMY. 

serted  as  above  mentioned  into  tlie  inner  small  trochanter. 
Externally  it  is  ir^  contact  with  the  origin  of 

Hectus  femoris.  This  muscle  combines  mth  the  two 
vasti  to  form  that  large  fleshy  mass  which  clothes  the  front 
of  the  femur,  by  some  anatomists  described  as  a  single 
muscle  under  the  term  triceps  extensor  cruralis,  since, 
being  inserted  l>elow  mto  the  upper  surface  of  the  patella, 
they  serve  through  the  medium  of  its  three  straight  liga- 
ments to  extend  the  tibia  on  the  femur.  Rectus  femoris 
arises  by  two  fiat  tendinous  bands  from  the  external  and 
internal  surfaces  of  the  neck  of  the  ilium  ;  between  these  is 
a  bursa  with  a  mass  of  fat.  It  passes  over  ilio-femoralis 
at  its  attachment  to  the  capsular  ligament  of  the  hip-joint, 
and  opposite,  about  the  centre  of  the  femur,  blends  with 
the  vasti. 

Vastus  externiis  arises  from  the  antero-extemal  part  of 
the  femur,  extending  as  high  up  as  trochanter  major,  oppo- 
site the  middle  third  of  the  femur  it  blends  with 

Vastus  interims,  which  is  attached  to  theantero-intemal 
part  of  the  superior  two  thirds  of  the  femur.  Between  it 
and  vastus  externus  superiorly  is  the  inferior  attachment  of 

Ilio-femoralis,  a  small  muscular  band  attached  supe- 
riorly to  the  front  of  the  neck  of  the  ilium,  below  the  heads 
of  rectus  femoris-,  passing  over  and  becoming  attached  to 
the  capsular  ligament  of  the  hip- joint,  which  it  prevents 
from  injury  during  movements,  and  becoming  inserted 
for  aboat  two  inches  and  a  half  along  the  upper  part  of  the 
central  line  of  the  front  of  the  femur.  It  thus  corresponds 
exactly  to  scapulo-humeralis  posticus  of  the  foi^  limb. 

In  the  attachments  of  the  "  triceps  cruralis"  to  the  patella 
are  distinguishable  several  synovial  bursse,  and  between 
rectus  femoris  and  vastus  internus  run  the  main  branch 
of  the  crural  nerve,  and  the  inguinal  artery  and  vein. 
These  parts  just  described  are  supplied  with  blood  by  the 
external  iliac  artery,  which  arises  from  the  posterior 
aorta,  where  it  passes  on  to  the  underneath  surface  of  the 
sacrum,  about  two  inches  before  it  breaks  up  to  form  the 
internal  iliac  arteries.  Just  at  its  origin  it  gives  off  the 
circumflex  artery  of  the  ilium,  which  runs  forwards  and 
downwards  to  the  antero-inferior  spinous  process  of  the 
ilium,  supi^lying  in  its  course  iliacus  and  proceeding  on 
inio  the  flank,  where  its  terminal  ramifications  anastomose 
with  those  of   the  lumbar,  intercostal,  internal  thoracis-. 


THE    HIND    EXTREMITY.  203 

and  epigastric  arteries.  The  artery  of  the  cord  (of  the 
male)  generally  arises  from  the  external  iliac  near  its 
commencement,  and  runs  to  the  internal  abdominal  ring, 
where  it  commences  to  -supply  the  structures  of  the 
posterior  part  of  the  spermatic  cord  ;  in  the  female  this 
artery  is  termed  the  uterine,  it  is  very  large  and  runs 
directly  backwards  to  supply  the  uterus,  being  much 
enlarged  in  pregnant  animals.  The  main  trunk  of 
the  external  iliac  continues  along  the  brim  of  the  pelvis 
and  about  one  and  a  half  inches  below  the  pectinean 
tubercle  it  breaks  up,  forming  the  arteria  profunda  femoris 
and  the  femoral  artery.  Arteria  profunda  femoris  passes 
in  a  direction  backwards,  but  gives  ofl'  the  epigastric  artery, 
which  runs  forwards.  It  then  passes  between  pectineus 
and  the  terminal  portion  of  psoas  magnus  and  iliacus 
above  trochanter  minor  internus,  then  externally  to  ischio- 
femoralis,  and  so  gains  triceps  abductor  femoris,  which  it 
mainly  supplies.  It  sends  a  long  branch  downwards  with 
the  sacro-sciatic  nerve  to  supply  biceps  rotator  tibialis  and 
ischio-tibialis.  The  epigastric  artery  arises  from  arteria 
profunda  femoris  about  half  an  inch  from  its  origin, 
courses  its  way  forwards  over  the  inner  surface  of  the 
femoral  artery  and  thus  gains  the  muscles  of  the  flank, 
where  its  terminal  ramifications  blend  with  those  of  the 
numerous  arteries  supplying  this  region,  while  one  of  its 
branches,  the  external  pudic,  passes  downwards,  and  after 
passing  through  the  external  abdominal  ring,  in  the  female 
supplies  the  mammary  gland  with  blood,  in  the  male  the 
penis,  breaking  up  to  form  the  anterior  dorsal  artery  of  the 
penis,  which  runs  forwards  towards  the  glans,  and  the 
posterior  dorsal  artery  of  the  penis,  which  runs  backwards 
to  anastomose  with  the  branches  of  the  internal  pudic 
branch  of  the  obturator  arter}^ 

The  femoral  artery  from  the  neck  of  the  ilium  passes 
downwards  over  the  internal  surface  of  the  insertion  of 
iliacus,  and  here  gives  off  the  inguinal  branch,  which  dips 
with  the  crural  nerve  between  rectus  femoris  and  vastus 
internus.  It  then  passes  over  the  inner  surface  of  the 
femur,  through  the  femoral  space,  giving  off  muscular 
branches  forwards  and  backwards  and  the  medullary  artery 
of  the  femur,  the  largest  medullary  artery  in  the  body.  It 
courses  its  way  between  the  insertions  of  pectineus  and  the 
short  head  of  biceps  adductor  femoris  on  the  one  side,  and 


264*  OUTLINES    OF    EQUINE   ANATOMY. 

the  internal  surface  of  vastus  internus  on  the  other,  then 
dips  between  the  two  portions  of  the  large  head  of  biceps 
adductor.  Thus  it  gains  the  posterior  part  of  the  femur, 
and  after  giving  off  a  large  branch  running  directly  hade- 
wards,  passes  between  the  internal  head  of  gastrocnemius 
externus  and  gastrocnemius  inter nus. 

After  giving  off  the  external  iliac  arteries,  the  posterior 
aorta  becomes  very  small  in  calibre,  and  after  running 
about  two  inches  on  the  under  surface  of  the  sacrum, 
breaks  up  to  form  two  internal  iliac  arteries,  between 
which  is  sometimes  seen  the  middle  sacral  artery.  The 
internal  iliacs  diverge,  running  in  a  downward,  outward, 
and  backward  direction,  giving  off  the  artery  of  the  hulb, 
and  termina^te  by  breaking  up  into  the  obturator,  gluteal, 
and  lateral  sacral  trunls.  The  artery  of  the  bulb,  almost 
at  its  origin  gives  off  the  umbilical  artery,  which,  pervious 
in  the  foetus,  in  the  adult  degenerates  into  an  impervious 
fibrous  cord,  w^hich  runs  to  the  central  part  of  the  fundus 
of  the  bladder  between  the  two  folds  of  the  broad  liga- 
ment of  that  organ.  It  is  termed  the  round  ligamerit  of 
the  bladder,  and  in  the  foetus  serves  to  carry  blood  to  the 
chorion  for  revivification.  After  giving  off  this  vessel  the 
artery  of  the  bulb  passes  along  the  side  of  the  pelvis,  gives 
off  a  large  branch  to  supply  the  bladder  and  prostate  gland, 
and  terminates  in  the  bulb  of  the  penis  ;  in  the  female  in 
the  erectile  walls  of  the  vagina.  It  gives  off  perineal 
branches,  which  supply  the  posterior  part  of  the  rectum 
and  the  anus,  anastomosing  with  branches  from  the  lateral 
sacral  and  internal  puclic  arteries. 

The  obturator  runs  from  its  origin  directly  over  the 
venter  surface  of  the  ilium  to  the  anterior  and  external  part 
of  the  obturator  foramen,  after  passing  through  which  it 
breaks  up  into  three  very  indefinite  branches  :  pmbic  runs 
forwards,  ischiatic  downwards,  and  the  internal  pudic  to 
the  bulb  of  the  penis,  breaking  up  in  the  erector  penis 
muscle,  and  anastomosing  anteriorly  with  the  posterior 
dorsal  artery  of  the  penis,  given  off  by  the  external  pudic 
branch  of  the  epigastric,  posteriorly  with  the  artery  of 
the  bulb.  While  pa'ssing  over  the  surface  of  the  ilium,  the 
obturator  gives  off  a  branch  which  passes  over  the  brim  of 
the  pelvis  just  above  the  origin  of  rectus  femoris,  and 
passes  mainly  between  that  muscle  and  vastus  externus  ;  it 
is  the  arteria  innominata. 


THE    HIND    EXTREMITY.  265 

The  gluteal  artery,  immediately  after  its  origin,  passes 
through  the  foramen  situated  between  the  posterior  margin 
of  the  ilium  and  the  anterior  margin  of  the  sacro- sciatic 
ligament.  It  then  breaks  up,  sending  large  branches  to 
the  gluteal  muscles,  and  among  others  a  remarkable  one 
running  along  the  lateral  margin  of  the  sacrum  between 
two  folds  of  the  ligament.  Thus  the  muscles  on  the  quarter 
are  supplied  with  blood. 

The  lateral  sacral  artery  passes  from  the  terminal  por- 
tion of  the  internal  iliac  in  a  backward  direction  along  the 
outer  margin  of  the  under  surface  of  the  sacrum  ;  thus  the 
artery  tends  to  approach  its  fellow.  It  terminates  poste- 
riorly in  giving  origin  to  vessels  running  to  the  tail  {lateral 
coccygeal  arteries).  Superiorly  it  gives  off  small  hrancJies 
to  the  spinal  cord,  which  pass  through  the  subsacral  fora- 
mina and  medullary  arteries  to  the  sacral  hones.  Inferiorly 
it  gives  off  hcemorrhoidal  branches  to  the  rectum,  w^hich 
anteriorly  anastomose  with  the  terminal  branches  of  the 
posterior  mesenteric,  posteriorly  with  the  artery  of  the  bulb 
and  its  branches. 

The  middle  sacral  when  present  runs  along  the  central 
line  of  the  under  surface  of  the  sacrum,  and  terminates  in 
giving  rise  to  the  middle  or  hiferior  coccygeal  artery. 

The  femoral  vein  exactly  corresponds  to  the  femoral 
artery  ;  just  above  the  trochanter  minor  internus  it  receives 
the  vena  saphena  (which  we  have  already  seen  coursing 
along  the  inner  surface  of  the  limb  from  the  hock,  subcu- 
taneously  placed).  Also  in  front  of  symphysis  pubis  it 
receives  the  transverse  branch  already  noticed.  It  termi- 
nates superiorly  in  forming  the  external  iliac  vein,  which 
unites  with  the  internal  iliac  vein  (which  brings  blood 
from  the  parts  supplied  by  the  artery  of  the  same  name) 
to  form  the  common  iliac  vein,  a  vessel  of  about  three 
inches  in  length,  which  combines  with  its  fellow  under  the 
last  lumbar  vertebra,  above  the  posterior  aorta,  to  form 
the  commencement  of  posterior  vena  cava.  This  vessel 
receives  the  circumflex  vein  of  the  ilium  ;  it  is  to  be  found 
between  the  external  and  internal  iliac  arteries.  The  pos- 
terior extremity  is  supplied  by  four  large  nerves  in  addi- 
tion to  small  sacral  branches  and  the  sympathetic  system ; 
these  are  the  crural,  gluteal,  sciatic,  and  obturator. 

Like  all  the  other  spinal  nerves,  those  in  the  lumbar 
region,  on    emerging  from  the  spinal  canal  through  the 


2(jQ  OUTLINES    OF    EQUINE    ANATOMY. 

intervertebral  gaps,  break  up  into  superior  and  inferior 
branches.  The  superior  branches  pass  upwards  to  supply 
longissimus  dorsi  and  the  other  muscles  in  the  lumbar 
region  of  the  back  ;  the  inferior  branches  break  up,  sending 
some  fibres  to  the  abdominal  muscles  running  over  trans- 
versal! s  abdominis  ;  others  to  the  psoae  muscles  ;  others 
from  the  second,  third,  fourth,  and  fifth  to  form  the  crural 
nerve,  which  passes  along  the  brim  of  the  pelvis,  and 
opposite  symphysis  pubis  breaks  up,  its  main  portion  run- 
ning between  rectus  femoris  and  vastus  internus  to  supply 
the  muscles  clothing  the  front  of  the  femur,  a  small,  long 
branch  (saphenous  nerve)  passing  downwards  with  vena 
saphena  subcutaneously  as  far  as  the  hock.  From  the  in- 
ferior branches  of  the  third  and  fourth  lumbar  nerves  the 
obturator  nerve  arises.  It  takes  the  same  course  as  the 
artery  of  the  same  name,  and  supplies  the  structures  on 
the  external  and  internal  surface  of  the  obturator  foramen 
and  ligament. 

The  sacral  nerves  differ  from  the  other  spinal  nerves  in 
that  they  run  in  an  oblique  direction  outwards  and  back- 
wards from  their  origin,  thus  forming  that  arrangement 
in  the  terminal  portion  of  the  spinal  or  vertebral  canal 
to  which  the  name  cauda  equina  has  been  given.  They 
also  divide  into  superior  and  inferior  branches  prior  to 
leaving  the  canal.  The  superior  branches  pass  in  an  upward 
direction  through  the  supersacral  foramina  to  supply  the 
anterior  portion  of  the  coccygeal  muscles  and  the  upper 
parts  of  the  muscles  of  the  quarter ;  the  inferior  branches 
run  to  supply  the  muscles  of  the  quarter,  fibres  from  the 
first  sacral,  and  the  last  lumbar  nerves,  combining  to  form 
the  gluteal  nerve,  which  passes  through  the  foramen  at 
the  anterior  part  of  the  sacro-sciatic  ligament  between  it 
and  the  ilium,  thus  gaining  the  external  surface  of  the 
ligament,  where  it  supplies  the  muscles  of  the  cjuarter.  The 
inferior  branches  of  the  last  lumbar,  with  the  first  three 
sacral  nerves,  combine  to  form  the 

Sciatic  nerve,  the  largest  in  the  body,  which,  by  passing 
with  the  gluteal,  gains  the  external  surface  of  the  sacro- 
sciatic  ligament,  over  which  it  runs  on  the  inner  surface 
of  triceps  abductor  femoris  over  the  neck  of  the  ischium, 
between  the  cotyloid  cavity  and  the  tuberosity  of  the 
ischium,  and  down  as  far  as  the  superior  extremity  of  the 
gastrocnemii  muscles.     In  its  course  behind  the  femur  it 


THE    HIND    EXTREMITY.  267 

is  accompanied  by  two  roots  of  vena  profunda  femoris,  and 
a  branch  of  arteria  profunda  femoris.  Inferiorlj  it  breaks 
up  to  form  the  anterior  and  iiosterior  tibial,  and  popliteal 
nerves.  In  its  course  down  the  limb  it  gives  off  fibres  to 
all  the  large  muscles  among  which  it  runs.  Bj  removal  of 
the  above-mentioned  structures  we  are  enabled  to  see 

Ischio-femoralis,  which  arises  from  the  under  surface  of 
the  neck  of  the  ischium,  and  becomes  inserted  with  the  ten- 
dinous band  of  triceps  abductor  femoris  to  the  posterior 
surface  of  the  femur  midway  between  the  two  small  tro- 
chanters ;  it  is  triangular  and  fleshy ;  also  the  four 
muscles  which  become  inserted  into  the  fossa  behind 
trochanter  major  are  thus  exposed ;  these  are 

Obturator  externus,  which  arises  from  the  under  surface 
of  the  obturator  ligament  and  the  margins  of  the  obturator 
foramen.  It  resembles  a  number  of  small  muscles  united 
together. 

Gemini  vel  iscMo-trochanterius,  composed  of  two  very 
similar  united  portions,  which  arise  from  the  under  surface 
of  the  neck  of  the  ischium  in  front  of  ischio-femoralis. 

Obturator  internus,  which  arises  within  the  pelvis  from 
the  upper  surface  of  the  obturator  ligament,  is  superiorly 
covered  by  a  reflection  inwards  of  the  sacro-sciatic  liga- 
ment and  is  also  attached  to  the  margins  of  the  obturator 
foramen.     This  muscle  combines  with 

Pyriformis,  arising  from  the  posterior  part  of  the  venter 
ilii,  as  high  up  as  the  transverse  process  of  the  first  sacral 
vertebra.  The  tendon  common  to  the  two  gains  exit  from 
the  pelvis  by  passing  between  the  sacro-sciatic  ligament 
and  the  neck  of  the  ischium  in  winding  round  the  bone, 
where  it  is  lubricated  by  synovia;  it  then  blends  with 
obturator  externus  and  gemini  in  passing  to  their  common 
insertion.  The  limb  may  now  be  removed  from  the  trunk 
by  sawing  through  the  middle  of  the  femur  transversely. 
The  gastrocnemii  muscles  may  then  be  examined. 
_  Gastrocnemius  externus  arises  by  two  heads  from  the 
ridges  bounding  the  fossa  on  the  postero-inferior  part  of 
the  femur  inclined  to  the  outer  side,  one  from  the  inferior 
third  of  the  external  surface,  the  other  from  the  inferior 
third  of  the  posterior  surface  of  that  bone.  The  external 
head  is  covered  by  a  hroad  aponeurotic  hand,  which  runs 
to  form  a  sheath  for  gastrocnemius  externus,  after  receiving 
a  band  from  the  aponeurosis  of  gracilis.     It  then  meets  a 


268  OUTLINES    OF    EQUINE    ANATOMY. 

funiculus  running  from  gastrocnemius  internus,  and  forms 
a  loop  through  which  plantaris  runs.  This  band,  plan- 
taris,  and  gastrocnemius  externus,  together  become  inserted 
into  the  point  of  the  hock,  after  playing  over  a  bursa. 
About  opposite  the  superior  j)art  of  the  inferior  third  of 
the  tibia  the  tendon  of  gastrocnemius  internus,  which  has 
been  hitherto  placed  in  front  of  the  externus,  winds  from 
within  oidivards  around  the  externus  tendon,  on  which  it 
plays  through  the  medium  of  a  synovial  sheath, 

Plantaris  is  a  fleshy  muscle,  apparently  too  long  for  its 
situation,  running  from  the  superior  part  of  the  fibula  to 
become  inserted  as  above  described  into  the  superior  part 
of   OS    calcis.     The   aponeurosis    of  the   lowest    head    of 
triceps  abductor  femoris  sends  downwards  a  broad  band  of 
white  fibrous  tissue  ;  some  of  the  muscular  fibres  of  biceps 
rotator  tibialis  terminate  in   tendinous  structure,   which 
blends  with  the  above ;    a  little   lower  down    this  band 
receives  fibres  from  gastrocnemius    internus.      About  an 
inch  and  a  half  above  the  point  of  the  hock  it  bifurcates, 
one  division  running  on  to  the  inner,  the  other  to  the  outer 
surface  of  the  point  of  os  calcis,  from  Avhich  they  pass  to 
the  dilated  portion  of  the  tendon  of   gastrocnemius   in- 
ternus, which  forms  the  cap  of  the  hock,  which  they  serve 
to  prevent  from  dislocation,  being  assisted  by  some  liga- 
mentous fibres  which  run  directly  from  the  cap  to  the  bone. 
Gastrocnemius  internus    arises  from  the  fossa  at  the 
postero-external  part  of  the  femur,  between  the  two  heads 
of  the  gastrocnemius  externus.     It  passes  over  the  posterior 
part  of  the  stifle  joint,  and  after  sending  some  tendinous 
structure    to    the   fibrous   band   running    to     the   hock, 
becomes  tendinous,  winds  round  the  tendon  of  the  external 
gastrocnemius  muscle   from  within  outwards,  and   then, 
widening,  forms  a  cap  for  the  point  of  os  calcis,  which  is 
retained  in  position  in  the  above-mentioned  manner  by  two 
fibrous  bands,  and  which  plays  over  a  large  synovial  bursa ; 
continuing  downwards  it  is  termed  the  perforatus  tendon, 
and  exactly  corresponds  to  that  of  the  fore  extremity. 

Popliteus  is  attached  inf  eriorly  to  a  triangular  roughened 
surface,  situated  on  the  inner  part  of  the  postero-superior 
region  of  the  tibia ;  its  fleshy  fibres  converge,  forming  a 
tendon  which  runs  in  an  outward  direction  over  the  surface 
of  the  capsular  ligament  of  the  stifle-joint  within  its  external 
lateral  ligament   (lubricated    with    synovia),  to    become 


THE    IIIXD    EXTREMITY.  2G9 

inserted  into  a  groove  between  the  outer  condyle  and  outer 
ridge  of  the  femur. 

Flexor  pedis  perforans  also  arises  from  the  posterior 
surface  of  the  tibia,  but  is  externally  placed,  being  also 
attached  to  the  posterior  margin  of  the  fibula ;  it  becomes 
tendinous  above  the  hock,  passes  over  the  concave  internal 
surface  of  os  calcis,  where  it  is  lubricated  with  synovia ; 
opposite  the  superior  third  of  the  large  metatarsal  bone 
receives  the  tendon  of  flexor  pedis  accessorius  and  the 
subtarsal  ligament,  which  is  not  so  strong  as  the  sub- 
carpal.  Below  this  it  comports  itself  in  a  manner  corre- 
sponding to  the  similar  tendon  of  the  fore  limb. 

Flexor  pedis  accessorius  arises  from  the  posterior  surface 
of  the  tibia,  between  the  attachments  of  popliteus  and  the 
perforans  ;  it  becomes  tendinous  oj^posite  the  inferior  third, 
and  passes  through  a  groove  situated  just  behind  the  inner 
malleolus  of  the  tibia,  where  it  is  bound  down  by  a  con- 
tinuation of  the  posterior  annular  ligament,  and  lubricated 
with  synovia,  having  a  sheath  which  extends  obliquely 
downwards  and  backwards  over  the  lateral  part  of  the 
hock.  It  terminates  in  becoming  blended  with  perforans, 
opposite  the  superior  third  of  the  large  metatarsal  bone. 
On  the  external  surface  of  the  limb  we  see  three  muscles. 

Peroneus  arises  from  the  outer  surface  of  the  fibula, 
being  continuous  superiorly  with  the  outer  lateral  ligament 
of  the  stifle-joint.  Its  fibres  converge  in  a  bipenniform 
manner  to  form  a  small  tendon,  which  passes  through  the 
groove  found  on  the  external  malleolus  of  the  tibia.  It  is 
here  lubricated  by  synovia,  and,  enclosed  in  a  synovial 
sheath,  passes  within  the  annular  ligament  in  an  oblique 
direction  forwards,  joining  extensor  pedis  tendon  with 
extensor  pedis  accessorius  at  the  inferior  part  of  the 
superior  third  of  the  large  metatarsal  bone. 

Flexor  metatarsi  arises  by  a  round  tendon  common  to 
it  and  to  extensor  pedis  from  the  depression  between  the 
outer  condyle  and  the  outer  ridge  of  the  femur.  This 
tendon,  after  becoming  attached  to  the  capsular  ligament, 
passes  in  the  groove  between  the  spine  of  the  tibia  and  the 
head  of  the  fibula,  where  it  plays  over  a  synovial  bursa ; 
it  then  gives  off  extensor  pedis,  and  receives  numerous 
muscular  fibres  from  their  attachment  in  the  external 
channel  of  the  tibia.  The  tendon,  however,  continues  as  a 
white  fibrous  band  to  the  front  of  the  hock,  where  it  breaks 


270  OUTLINES    OF    EQUINE    ANATOMY. 

up  to  become  inserted  into  several  of  the  small  bones  of 
that  joint,  while  the  tendons  of  the  muscular  portion  pass 
between  its  divisions,  thus  completing  its  inferior  attach- 
ment to  all  the  small  bones  of  the  hock,  directly  or  indi- 
rectly, and  to  the  upper  part  of  the  three  metatarsal  bones. 
With  one  of  these  tendons  the  middle  band  of  the  anterior 
annular  ligament  of  the  hock  blends. 

Extensor  pedis,  arising  from  the  originating  portion  of 
the  tendinous  part  of  flexor  metatarsi,  as  above  indicated, 
passes  down  the  front  of  the  hock,  and  through  its  three 
anterior  annular  ligaments,  lubricated  by  synovia.  After 
receiving  the  tendons  of  peroneus  and  extensor  pedis 
accessorius  opposite  the  inferior  part  of  the  superior  third 
of  OS  metatarsi  magnum,  it  comports  itself  as  does  the 
extensor  pedis  of  the  fore  limb. 

Extensor  pedis  accessorius  arises  from  the  front  of 
astragalus  below  its  articular  ridges,  and  joins  extensor 
pedis,  which  covers  it  from  its  origin,  bein  g  slightly  visible 
between  it  and  peroneus. 

The  terminal  portion  of  the  femoral  artery  passes 
between  the  two  heads  of  gastrocnemius  externus,  and 
then  between  its  internal  head  and  the  head  of  ga.strocne- 
mius  iuternus.  It  sends  off  a  hrancJi  ichich  runs  doiunwards 
behveen  the  huo  gastrocnemii,  and  then  passes  between  the 
condyles  of  the  femur  to  break  up  behind  the  stifle-joint, 
forming  the  anterior  and  the  posterior  tibial  arteries. 

The  posterior  tibial  artery  runs  down  the  posterior  sur- 
face of  the  tibia,  at  first  between  popliteus  and  the  bone, 
subsequently  between  flexores  pedis  j)erforans  and  acces- 
sorius. It  becomes  superficial  at  the  supero -internal  part 
of  the  hock,  and  here  makes  its  sigmoid  flexure,  by  which, 
in  terminating,  it  anastomoses  superiorly  with  the  arterial 
branch  between  the  gastrocnemii,  inferiorly  with  the  recur- 
rent branch  of  the  metatarsal  artery.  It  supplies  the 
muscles  and  skin  at  the  posterior  part  of  the  tibia,  and 
the  medullary  artery  of  that  bone  at  the  inferior  part  of 
its  superior  third. 

The  anterior  tibial  artery  runs  in  a  forward  direction 
from  its  origin,  and  passes  between  the  tibia  and  the  fibula, 
and  thus  underneath  jDeroneus  to  gain  the  front  of  the 
limb,  down  which  it  passes  underneath  flexor  metatarsi 
and  extensor  pedis,  which  it  supplies.  At  the  front  of  the 
hock   it   passes  through  an  oblique   groove  at  the  outer 


THE    HIND    EXTREMITY.  271 

part  of  the  superior  extremity  of  the  large  metatarsal 
bone,  and  thus  gains  the  channel  between  this  bone  and 
the  extei'nal  small  metatarsal,  in  which  it  runs  subcuta- 
neously,  so  that  the  pulse  may  be  taken  here.  It  passes 
between  the  inferior  extremity  of  the  small  bone  and  the 
large  bone  to  gain  the  posterior  part  of  the  inferior  third 
of  the  latter,  where,  after  giving  off  the  recurrent  branch, 
it  bifurcates  in  passing  between  the  divisions  of  the  supe- 
rior sesamoideal  ligament,  forming  plantar  arteries  ana- 
logous in  situation  and  distribution  to  those  of  the  fore 
limb.  The  recurrent  branch  passes  up  the  back  of  the 
OS  metatarsi  magnum,  protected  by  the  inner  small  meta- 
tarsal bone,  and  at  the  inferior  part  of  the  superior  third 
gives  off  tlie  medullary  artery  of  the  large  metatarsal  hone.  It 
terminates  at  the  supero-internal  part  of  the  hock,  by  anas- 
tomosing with  the  posterior  tibial  at  its  sigmoid  flexure. 

The  superficial  metatarsal  vein  runs  on  the  inner  sur- 
face of  the  limb  in  the  groove  between  the  large  and  inner 
small  metatarsal  bones.  At  the  front  of  the  hock  it  bifur- 
cates ;  one  branch  runs  on  to  the  internal  surface  of  the 
tibia,  forming  the  commencement  portion  of  the  vena 
saphena,  the  other,  by  uniting  with  a  large  branch  running- 
from  between  the  bones  of  the  hock,  forms  the  anterior 
tibial  veins,  generally  two  in  number,  one  of  them  beings 
enlarged,  the  varicose  vein  of  the  thigh,  they  pass  with  the 
artery  of  the  same  name.  The  deep-seated  metatarsal 
veins  divide  superiorly  ;  one  division  forming  the  inter^ 
osseous  branch,  which  passes  between  the  bones  of  the  hock 
to  assist  in  forming  the  anterior  tibial,  the  other  passincr 
through  the  groove  of  the  calcis  to  form  the  posterior 
tibial  veins,  which  accompany  the  arteries  of  the  same 
name  up  the  back  of  the  til3ia. 

Just  above  the  commencement  of  the  gastrocnemii 
muscles  the  sacro- sciatic  nerve  terminates  in  breaking 
up  to  form  the  anterior  and  posterior  tibial,  and  pojAiteal 
nerves.  The  popliteal  proceeds  down  the  back  of  the 
limb,  and  dips  between  popliteus  and  the  flexors,  which 
it  supplies  with  nerve  force.  The  anterior  tibial  passes 
over  the  external  head  of  gastrocnemius  externus  and 
peroneus  to  gain  the  muscles  in  front  of  the  tibia  It 
thus  presents  a  marked  difference  in  its  course  as  com- 
pared with  that  of  the  artery  and  vein  of  the  same 
name.     It  is  sometimes  divided  at  its  superficial  part  by 


272  OUTLINES    OF   EQUINE    ANATOMY. 

the  operation  of  neurotomy.  To  expose  it,  only  skin, 
fascliia,  and  aponeurosis  of  triceps  abductor  fenioris  re- 
quire to  be  divided.  The  posterior  tibial  nerve,  dipping 
between  the  internal  head  of  gastrocnemius  externus  and 
gastrocnemius  internus,  follows  the  course  of  its  corre- 
sponding artery  over  the  back  of  the  stifle-joint,  and  run- 
ning down  the  posterior  surface  of  the  femur  between  the 
gastrocnemius  and  perforans,  just  above  the  hock,  divides 
to  form  the  external  and  internal  metatarsal  nerves,  which, 
after  passing  with  the  perforans  tendon  over  tlie  inner 
surface  of  os  calcis,  separate  and  take  a  course,  and  give  off 
branches  exactly  as  the  metacarpal  nerves  do  in  the  fore  limb. 

In  the  space  just  above  the  heads  of  the  gastrocnemii 
muscles  lie  the  popliteal  lymphatic  glands.  It  will  thus 
be  seen  that  the  hind  limb  below  the  hock  very  closely 
resembles  the  fore  limb  below  the  knee  ;  besides  the  differ- 
ences between  the  pedal  and  the  cannon  bones  of  the  fore 
and  hind  limb,  the  hoofs  differ,  those  of  the  hind  limb  being 
smaller,  more  upright,  and  having  their  ground  surface 
much  longer  than  broad,  and  more  concave,  with  thicker 
soles  than  those  of  the  fore. 

The  coccygeal  muscles  I'equire  a  passing  notice. 

Levator  coccygis  arises  from  the  lateral  part  of  the 
sacrum  between  the  superior  spinous  and  transverse  pro- 
cesses, blending  anteriorly  with  longissimus  dorsi.  It 
passes  backwarcls,  and  its  several  fasciculi  become  attached 
to  the  rudimentary  transverse  processes  of  the  coccygeal 
vertebrae.     It  is  covered  by  a  layer  of  faschia. 

Curvator  coccygis  arises  from  the  postero-lateral  and 
inferior  part  of  the  sacrum,  and  its  fibres  and  fasciculi  run 
along  the  lateral  part  of  the  tail ;  they  are  separated  from 
levator  coccygis  anteriorly  by  faschia. 

Compressor  coccygis  is  a  broad  square  muscle,  which 
extends  from  the  inner  surface  of  the  sacro- sciatic  ligament 
to  the  transverse  processes  of  the  two  or  three  anterior 
coccygeal  bones. 

Depressor  coccygis  is  attached  to  the  under  surfaces  of 
the  anterior  coccygeal  bones,  its  fibres  pass  downwards 
towards  the  anus  and  become  confounded  with  those  of 
levator  ani. 

The  tail  is  supplied  with  blood  by  the  lateral  and  middle 
coccygeal  arteries,  with  nerve  force  by  coccygeal  branches 
from  the  posterior  part  of  the  spinal  cord. 


THE    FOOT.  27o 


PART  X.— SPECIAL  ANATOMY. 

The  Foot. 

CoN^siDERED  zoologically  tlie  foot  of  the  horse  compre- 
hends all  those  structures  placed  below  the  inferior  ex- 
tremity of  the  tibia  ;  the  point  of  os  calcis  corresponds  to 
the  heel  of  the  human  subject.  From  the  tarsus  the 
metatarsals  run  downwards  ;  their  normal  number  in  mam- 
malia is  five,  in  the  horse,  however,  we  find  but  three,  for 
the  inner  digit  is  absent  and  the  two  central  ones  coalesce. 
The  outer  of  the  three  in  the  fossil  forms  of  the  horse 
present  hoofs,  and  other  structures  found  in  the  existing 
forms  only  in  connection  with  the  double  central  digit.  In 
some  cases  even  in  the  present  day,  however,  we  find  a 
rudimentary  hoof  produced  below  one  of  the  metacarpal 
or  metatarsal  splint  bones,  in  rare  cases  ;  generally  these 
bones  terminate  inferiorly  in  a  slight  bulbous  enlargement. 
It  is,  then,  with  the  double  central  digit  we  have  here  to 
deal ;  its  comj^osition  of  two  similar  parts  is  shown  by  its 
symmetry,  and  by  a  depression  well  marked  in  some  cases 
at  the  antero- inferior  part  of  the  toe  of  os  pedis.  Again, 
in  all  cases  the  frog  is  divided  into  two  similar  portions  by 
a  deep  fissure,  the  cleft,  and  often  we  see  a  projection  on 
the  inner  surface  of  the  hoof  opposite  the  depression  in 
the  toe  of  os  pedis  just  at  the  point  of  junction  of  the 
wall  and  the  sole  of  the  hoof.  That  portion  commonly 
known  as  the  foot,  consists  of  a  horny  box  with  its  con- 
tents. The  horny  box  corresponds  to  the  nail  of  the  toe 
of  the  human  subject  with  the  thickened  skin  on  the  sole 
of  the  foot,  while  the  contents  comprise  certain  bones  with 
their  appendages  covered  by  a  layer  of  highly  vascular 
tissue,  which  corresponds  to  the  true  skin,  and  which  pro- 
duces the  horn,  which  is  analogous  with  the  epidermis  or 
cuticle.  The  HOOF  is  separable  from  the  other  structures 
by  maceration  by  a  continuation  of  this  process  it  may  be 

18 


274  OUTLINES    OP    EQUINE    ANATOMY. 

separated  into  minor  parts,  we  generally  see  it  as  a  horny 
box  presenting  an  opening  above.  It  is  composed  of  epi- 
thelial cells,  being  (as  before  observed)  merely  epidermis 
so  modified  as  to  form  the  substance  commonly  known  as 
horn.  Horn  consists  of  tubular  processes  similar  to  hairs 
united  by  softer  epithelial  cells,  the  latter  forming  a  matrix 
for  the  fibres  and,  by  fixing  them  firmly  together  giving  the 
horn  its  consistency.  The  horn  of  the  hoof  presents  two 
parts  with  different  characters.  The  horny  frog  is  much 
softer  in  consistency  and  more  elastic  than  the  remainder 
of  the  hoof,  and  resembles  in  nature  and  structure  (as 
pointed  out  by  Professor  Gamgee)  the  foot  pad  of  the  dog. 
It  owes  its  peculiarities  to  the  delicacy  of  its  horn  fibres, 
which  are  finer  than  those  of  most  other  parts  of  the  hoof, 
and  which  are  produced  by  the  delicate  papillae  of  the  sen- 
sitive frog.  The  hoof  consists  of  several  parts  agglutinated 
together  in  the  same  manner  though  less  firmly  than  the 
individual  fibres.  These  are  the  wall  (with  the  bars),  sole, 
and  frog.  The  frog  and  the  sole  are  separable  by  mace- 
ration, but  the  bars  are  mere  reflections  forward  and 
inwards  of  the  wall,  and  therefore  remain  firmly  fixed  to 
that  part.  The  Wall  is  all  that  portion  of  the  hoof  which 
is  visible  from  before  and  from  the  sides  when  the  foot 
rests  upon  its  plantar  surface.  It  is  artificially  divided  into 
six  parts,  three  on  each  side.  The  anterior  or  toe  centrally 
lies  in  connection  with  its  fellow,  externally  is  continuous 
with  the  quarter  or  middle  part  at  its  anterior  part,  while 
the  posterior  margin  of  the  quarter  is  continuous  with  the 
heel,  from  the  posterior  margin  of  which  the  bars  run  in  a 
direction  forwards  and  inwards  for  about  two  inches,  being 
separated  from  the  frog  by  the  commissures,  terminating 
anteriorly  in  a  point.  In  all  jjarts  the  fibres  of  the  hoof  run 
obliquely  downwards  and  forvmrds.  The  toe  and  the  pos- 
terior margin  of  the  heel  have  the  same  direction,  the 
latter  being  not  half  so  high  as  the  former  in  a  well-foi-med 
hoof ;  their  superior  extremities  are  connected  by  a  thin 
ridge  running  obliquely  downwards  and  backwards,  their 
inferior  margin  is  horizontal.  The  internal  surface  of  the 
wall  superiorly  presents  a  concave  surface  extending 
obliquely  downwards  and  backwards  about  half  an  inch  in 
depth,  growing  broader  posteriorly  in  becoming  inflected 
forwards  to  form  the  crust  of  the  bars  which  blend  with  the 
horny  sole  anteriorly.     It  presents  a  number  of  deep  small 


THE    FOOT.  2T5 

foramina,  into  whicli  the  papillae  of  tlie  vascular  coronary 
secreting  substance  pass.  The  wall  is  divided  into  crust 
and  horny  Jamince  ;  the  horny  laminae  are  leaf-like  plates 
projecting  from  the  inner  surface  of  the  crust,  taking  a 
direction  corresponding  to  the  fibres  of  the  wall,  commenc- 
ing superiorly  at  the  inferior  margin  of  the  above  men- 
tioned perforated  surface.  They  are  longest  at  the  toe 
and  become  insensibly  merged  in  the  wall  at  the  anterior 
extremity  of  the  bars.  Between  each  pair  of  these  in  the 
fresh  subject  for  the  greater  part  of  their  length  lies  a  sen- 
sitive lamina,  and  the  surfaces  of  the  horny  laminae  present 
foramina  into  which  pass  papillae  from  the  sensitive  coun- 
terpart. The  outer  utargm  of  each  lamina  is  continuous 
with  the  crust,  the  inner  is  free.  The  superior  extremity 
terminates  in  a  point  in  blending  with  the  above  described 
concave  surface,  the  inferior  terminates  on  the  ground  sur- 
face at  the  line  of  junction  of  the  wall  with  the  sole,  at  which 
part  the  outer  laminated  edge  of  the  sole  fits  between  the 
horny  laminae  as  the  sensitive  laminae  do  in  other  parts  ; 
the  extent  of  this  junction  depends  upon  the  variable 
thickness  of  the  sole.  The  horny  laminae  are  produced  by 
the  sensitive  laminae,  and  the  crust  by  the  coronary  secret- 
ing substance  ;  in  consequence,  therefore,  of  the  constant 
additions  to  its  thickness  the  wall  has  a  tendency  to 
greater  bulk  in  its  lower  than  in  its  upper  part.  That 
portion  of  the  wall  situated  at  the  extreme  superior  edge, 
which  is  secreted  by  the  line  of  vascular  substance  which 
presents  very  minute  papillae  and  seems  to  be  the  first  stage 
of  change  in  the  character  of  the  skin,  thus  presents  fibres 
more  delicate  than  those  of  the  rest  of  the  wall,  correspond- 
ing to  those  of  the  frog,  extending  for  but  a  short  distance 
downwards,  about  half  an  inch.  It  is  narrowest  anteriorly 
and  becomes  deepest  at  the  heels  in  blending  with  the  frog. 
This  is  the  coronary  frog  band  of  Bracy  Clark  (the  original 
specimen  of  this  by  Bracy  Clark  in  the  museum  of  the 
Eoyal  Veterinary  College  is  much  too  thick  anteriorly, 
where  a  small  portion  of  coarser  substance  has  been  left) . 
The  wall  is  thickest  at  the  toe,  it  gradually  decreases  in 
thickness  towards  the  heels,  and  again  increases  slightly  at 
the  extreme  posterior  part,  where  it  is  inflected  forwards 
to  form  the  bars.  In  no  part  is  the  wall  so  thin  as  the 
coronary  frog  band  at  the  extreme  superior  part.  The 
angle  the  toe  of  the  hoof  should  make  with  the  ground  has 


276  OUTLINES    OF    EQUINE    ANATOMY. 

been  stated  as  50°  in  a  good  foot,  but  it  is  influenced  loj 
various  causes,  as  breed,  age,  period  since  last  shoeing,  &c. 
Low  bred  horses  have  a  small  angle,  in  better  bred  horses, 
mules,  and  asses  it  is  less  acute.  The  obliquity  decreases 
towards  the  quarter  and  is  reversed  at  the  heels,  where  the 
posterior  line  of  the  plantar  surface  is  in  front  of  the  per- 
pendicular let  fall  from  the  extreme  posterior  part  of  the 
coronet.  The  obliquity  is  downwards  and  outwards  at  the 
bars.  The  inner  quarter  is  more  upright  than  the  outer,  and 
the  wall  on  the  inner  side,  taken  as  a  whole,  is  thinner 
and,  therefore,  more  readily  yields  to  superincumbent 
weight. 

The  horny  sole  presents  two  surfaces  and  two  margins, 
which  posteriorly  form  four  projections.  It  is  crescent 
shaped,  having  its  outer  circuwf event  margin  attached  to  the 
inner  surface  of  the  inferior  margin  of  the  wall.  Its  pos- 
ter o-iiitemal  part  is  fitted  into  the  horny  laminse  of  the 
bars,  and  continuous  with  the  crust  of  the  bars,  while  the 
central  part  of  the  posterior  margin  is  occupied  by  the  horny 
frog,  which  forms  a  wedge-shaped  projection  into  it  ex- 
tending to  within  about  two  inches  of  the  toe.  The  inferior 
surface  is  concave,  varying  in  degree  in  different  feet,  but 
it  presents  a  general  slant  from  the  outer  margin  upwards 
to  the  inner.  It  is  covered  by  scales  of  horn,  for  it  consists 
of  a  number  of  short  coarse  fibres  matted  together,  which, 
after  attaining  a  certain  length,  desquamate  regularly. 
The  union  of  the  sole  with  the  wall  is  by  projection  of  its 
substance  between  the  horny  lamina,  and  union  of  the  two 
by  connecting  epithelial  cells,  forming  a  marked  line  of 
junction,  softer  in  consistency  than  the  rest  o-f  the  hoof 
and  more  friable.  It  will  be  observed  that  the  fibres  of 
the  sole  run  like  those  of  the  crust,  obliquely  downwards 
and  forwards  in  all  parts.  The  union  with  the  anterior 
extremity  of  the  frog  is  simply  by  epithelial  cells.  The 
upper  surface  of  the  sole  is  convex,  an  exact  counterpart  of 
the  lower,  presenting  foramina,  into  which  the  papillae  of 
the  sensitive  sole  project,  and  which  are  most  marked 
centrally. 

The  Lorny  frog  is  situated  on  the  middle  line  of  the 
hoof  at  the  posterior  part.  It  is  a  wedge-shaped  body, 
having  its  base  posteriorly,  its  apex  anteriorly  placed,  ex- 
tending to  within  two  inches  of  the  toe  of  the  foot.  It 
presents  two  lateral  margins,  which  anteriorly  are  attached 


THE    FOOT.  277 

to  tlie  liornj  sole,  posteriorly  to  the  horiij  bars,  and  at  the 
posterior  angles  are  continuous  with  the  coronary  frog  band. 
The  posterior  margin  becomes  very  thin,  blending  with  the 
epidermis  of  the  skin  of  the  heels.  The  frog  bulges  oa  the 
ground  surface  of  the  foot,  presenting  anteriorly  a  rounded 
angle  or  apex,  and  posteriorly,  at  the  base,  two  rounded 
prominences  termed  the  bulbs,  separated  by  the  cleft,  which 
extends  more  than  half  the  length  of  the  frog  in  a  forward 
direction,  being  widest  posteriorly,  terminating  in  a  point 
anteriorly  on  the  ground  surface.     The  bulbs  of  the  froo- 


are  separated  from  the  bars  by  the  commissures,  deep  fis- 
sures readily  noticeable.  The  u]3per  surface  of  the  frog  is 
the  exact  counterpart  of  the  lower,  presenting  centrally  a 
peculiar  high  prominence,  terminating  superiorly  in  a 
rounded  point,  which  fits  into  the  cleft  of  the  fibrous  frog 
(covered  by  its  vascular  coat) .  This  is  termed  the  frog- 
stay  or  peak,  and  on  either  side  of  it  lies  a  concavity, 
widest  posteriorly,  by  its  elevated  outer  margin  blending 
with  the  bars  and  sole.  The  two  concavities  run  together 
anteriorly,  terminating  in  a  point.  This  surface  presents 
small  foramina  for  the  delicate  papillae  of  the  sensitive 
frog,  least  marked  on  the  most  prominent  portions.  The 
fibres  of  the  frog  run  obliquely  downwards  and  forwards. 
The  colour  of  the  hoof,  in  general,  depends  upon  that  of 
the  sensitive  structure  by  which  it  is  2)i'oduced ;  thus,  in 
horses  with  white  coronets  it  is  generally  white,  but  any 
coloration  of  the  coronet  is  marked  by  corresponding  colour 
of  the  hoof  below  this  point,  extending  from  above  towards 
the  ground  surface,  varying  in  length  in  direct  proportion 
to  the  superficiality,  or  otherwise,  of  the  pigmentary 
deposit. 

The  hoof  of  the  fore  foot  is  marked  by  the  roundness  of 
the  plantar  surface,  broken  posteriorly  by  the  space  for  the 
frog ;  also  by  the  obliquity  of  its  walls,  which  are  thickest 
at  the  toe,  and  decrease  in  thickness  towards  the  heels. 
The  distances  from  the  centre  of  the  toe  to  the  extremity 
of  each  heel  should  be  equal,  and  also  equal  to  the  broadest 
transverse  diameter.  The  inner  half  of  the  sole  is  generally 
smaller  and  narrower  than  the  outer ;  the  inner  quarter  is 
the  most  upright,  and  is  thinner  in  the  wall  than  the 
outer. 

The  hind  hoof  is  ovoid,  having  its  long  diameter  from 
behind  forwards.     It  is  wide  at  the  posterior  part  of  the 


278  OUTLINES    OF    EQUINE    ANATO:\IY. 

quarters,  while  their  anterior  part  is  rather  flat.  The  hoof 
in  general  is  more  upright  than  the  fore ;  the  thickest  horn 
is  at  the  quarters,  and  the  sole  is  very  concave,  the  frog 
being  smaller  and  narrower.  The  heels  also  are  longer 
than  those  of  the  fore  foot. 

The  sensitive  structures  of  the  foot  are  generally  exposed 
by  heating  the  foot  in  a  forge  fire,  removing  the  heated 
horn  from  the  outer  margin  of  the  plantar  surface  of  the 
foot  by  means  of  a  drawing  knife,  as  far  down  as  the  sen- 
sitive structures,  and  wrenching  the  wall  and  sole  thus 
separated  off  by  means  of  pincers,  the  foot  having  been 
fixed  in  a  vice.  The  frog  will  be  removed  with  the  sole. 
Some  art  is  required  in  the  operation,  slow  traction  being 
preferable  to  sudden  jerks.  By  this  means  we  expose  a 
red  and  highly  vascular  structure,  investing  the  digit  from 
the  coronet  downwards.  Opposite  the  centre  of  the  external 
surface  of  the  lateral  cartilage,  extending  round  the  foot 
anteriorly  and  posteriorly,  is  a  line  marking  where  the 
skin  commences  to  change  its  characters.  The  epidermis 
at  first  becomes  soft  and  light  in  colour,  and  then  modified 
to  form  the  hoof,  some  hairs  from  the  coronet  being  em- 
bedded in  the  white  cheesy  upper  rim  of  the  hoof.  The 
ordinary  skin  terminates  in  a  regular  and  well-marked 
line,  light  in  colour,  covered  with  fine  papillae,  and 
growing  wider  at  the  posterior  part,  becoming  blended 
with  the  bulbs  of  the  sensitive  frog.  Below  this,  ex- 
tending in  a  downward  direction  for  about  half  an  inch, 
is  the 

Vascular  layer  of  the  coronary  secreting  substance.  It 
gradually  decreases  in  size  in  a  direction  backwards,  more 
so  on  the  inner  than  on  the  outer  side,  and  at  the  posterior 
part,  against  the  bulbs  of  the  frog,  it  terminates  in  an 
acute  point,  being  thickest  just  before  this,  in  consequence 
of  its  inflection  forwards  to  join  with  the  vascular  sole, 
towards  which  it  runs,  being  here  about  two  inches  in 
length,  a  quarter  of  an  inch  in  width,  separating  the  sensi- 
tive laminae  of  the  bars  from  the  sensitive  frog.  It  differs 
slightly  from  the  above  description  in  the  hind  foot,  in 
accordance  with  the  different  shape  of  the  hoof.  The  vas- 
cular or  sensitive  coronary  secreting  substance  is  covered 
with  papillae,  which  are  minute  superiorly,  but  inferiorly 
become  very  marked.  In  some  cases  a  few  may  be  seen 
running  from  the  upper  part  of  the  vascular  laminae, 


THE    FOOT.  279 

whicli  are  thin  plates  covering  tlie  remainder  of  the  antero- 
lateral surface  of  the  basement  structure  of  the  foot,  run- 
ning from  above  downwards,  at  the  anterior  jmrt  meeting 
the  ground  surface  at  right  angles,  becoming  oblique 
laterally.  This  obliquity  from  behind  forwards  and 
downwards  increases  towards  the  heels,  the  laminae  also 
becoming  shorter  in  proportion.  At  the  heels  this  layer 
is  reflected  forwards,  slightly  inwards,  for  about  one  and  a 
half  inches  between  the  heel  of  the  sole  and  the  anterior 
inflection  of  the  vascular  coronary  secreting  substance, 
anteriorly  and  inferiorly  blending  with  the  sole,  terminating 
in  an  ill- defined  point,  for  here  we  see  a  useful  indication 
of  the  nature  of  the  lamince,  the  fact  that  they  are  linear 
rows  of  papillae  united  together  for  a  specific  purpose  being 
here  demonstrable.  By  careful  examination  we  may  see 
secondary  papillce  extending  horizontally  into  the  inter- 
spaces between  the  laminae  from  the  surfaces  of  the  layers. 
These  laminae  are  500  to  600  in  number ;  they  are  smallest 
superiorly,  where  they  commence  in  blending  with  the  coro- 
nary secreting  substance ;  inferiorly  they  blend  gradually 
with  the  sensitive  sole. 

The  sensitive  sole  covers  the  whole  of  the  plantar  sur- 
face of  OS  pedis,  with  the  exception  of  a  small  wedge- 
shaped  portion  running  forwards  from  the  centre  of  the 
posterior  crescentic  margin,  which  is  occupied  by  the  apex 
of  the  sensitive  frog.  At  the  anterior  jjart  also,  centrally, 
we  find  in  most  feet  a  marked  notch,  so  that  the  sensitive 
sole  is  narrowest  centrally,  and  from  this  gradually  in- 
creases in  width  to  the  anterior  part  of  the  laminae  of  the 
bars,  where  it  bifurcates ;  the  outer  division  terminating 
in  a  point  at  the  inflection  of  the  laminae  ;  the  inner  divi- 
sion blends  with  the  termination  of  the  coronary  secreting 
substance.  The  whole  surface  presents  papillae,  which 
around  the  outer  margin  are  small  and  continuous  with 
the  inferior  extremities  of  the  sensitive  laminae.  They 
gradually  increase  in  size  to  the  central  line  and  then 
again  decrease,  being  absent  at  the  line  of  junction  of  the 
frog  with  the  sole.  The  apex  of  the  frog  extends  to  within 
an  inch  of  the  toe  of  the  sole. 

The  sensitive  frog  covers  the  external  surface  of  the 
fibrous  frog,  and  consequently  presents  two  prominent 
ridges  running  from  behind  forwards,  obliquely  inwards, 
meeting  at  about  the  centre^  and  continued  on  to  form  a 


280  OUTLINES    or   EQUINE    ANATOMY. 

very  acute  angle  at  the  apex.  These  are  separated  by  the 
cleft,  and  on  either  side  laterally  blend  with  the  sensitive 
sole.  On  the  ridges  are  very  marked  papillae,  which  gra- 
dually decrease  in  size  in  extending  from  the  prominences 
until  they  are  absent  at  the  line  of  junction  with  the  sole. 
There  is  a  slight  line  caused  by  diminution  in  size  of  the 
papillae,  mapping  out  the  boundary  of  the  commissures.  It 
may  be  noticed  that  the  papillae  of  the  frog  are  smaller 
than  those  of  the  sole  and  of  the  coronary  secreting  sub- 
stance. The  vascular  horn-secreting  layer  in  all  parts 
consists  of  loose  areolar  tissue,  with  very  numerous  vessels 
ramifying  through  it.  The  vascular  sole  is  connected  to 
iKe  bone  by  loose  areolar  tissue,  in  which  is  situated  a 
plexus  of  veins,  and  the  solar  arteries  running  from  the 
artery  of  the  frog  outwards  in  a  radiating  manner  to  the 
circumflex  artery  of  the  toe,  which  runs  round  the  outer 
circumferent  margin  of  the  plantar  surface  of  os  pedis. 
The  sensitive  laminae  are  connected  by  denser  areolar 
tissue,  which  attaches  them  to  the  antero -lateral  surface 
of  OS  pedis,  where  they  cover  the  lateral  laminal  arteries 
and  the  branches  they  send  upwards  to  the  superficial 
coronary  artery,  and  downwards  to  the  circumflex  artery 
of  the  toe.  The  sensitive  layer  of  the  coronary  secreting 
substance  is  firmly  attached  to  a  somewhat  dense  band  of 
substance  (fibrous  coronary  band)  which  extends  round 
the  coronet.  This  is  deepest  at  the  toe,  where  it  is  attached 
to  extensor  pedis  tendon  at  its  insertion  ;  laterally  it  rests 
on  the  centre  of  the  lateral  cartilage  (external  surface), 
and  posteriorly  it  terminates  in  blending  with  the  fibrous 
or  fatty  frog.  This  is  an  elastic  substance,  occupying  the 
centre  of  the  posterior  part  of  the  foot.  It  consists  of  a 
quantity  of  yellow  elastic  tissue  arranged  in  fibres,  which 
interlace  in  all  directions,  but  the  largest  of  which  take  a 
direction  obliquely  from  above  downwards  and  forwards. 
In  the  meshes  of  these  fibres  is  a  quantity  of  substance 
apparently  of  a  fatty  nature,  whence  this  organ  has 
received  the  name  of  fatty  frog.  It  is  a  wedge-shaped 
body  with  two  surfaces,  a  base  and  an  apex.  The  S2iperior 
surface  lies  in  contact  with  the  under  surface  of  the  ex- 
panded perforans  tendon,  with  the  intervention  of  a  thin 
fibrous  layer.  It  extends  forwards  on  co  the  plantar  sur- 
face of  OS  pedis  at  the  posterior  crescentic  margin  at  its 
centre,  where  it  forms  a  triangular  projection.     Its  hase 


THE  rooT.  281 

becomes  blended  posteriorly  witli  the  corium  of  tbe  skin 
of  the  heels,  and  laterally  receives  the  termination  of  the 
coronary  fibrous  band.  The  apex  extends  to  within  about 
one  inch  of  the  toe  of  the  os  pedis.  The  lateral  parts 
superiorly  are  separated  from  inner  surface  of  the  lateral 
cartilage  by  means  of  a  plexus  of  veins ;  inferiorly  are 
firmly  attached  to  the  inflections  of  the  cartilages,  the 
transition  between  the  two  structures  being  gradual.  The 
inferior  surface  presents  a  figure  analogous  to  that  of  the 
under  surface  of  the  horny  frog,  which  is  moulded  upon 
it  with  the  intervention  of  the  vascular  frog.  It  therefore 
presents  two  hulbs  separated  from  each  other  by  a  cleft, 
which  form  the  base,  and  which  converge  anteriorly, 
and  are  continued  forward  to  terminate  in  a  point,  the 
aj^ex. 

We  now  come  to  the  basement  structure  of  the  foot, 
the  several  parts  composing  which  we  must  now  examine. 
The  bones  in  the  foot  are,  os  pedis,  os  navicular e,  and  the 
inferior  extremity  of  os  coronce. 

OS  CORONA,  though  broader  than  long,  and  possessing 
no  medullary  canal,  is  generally  considered  to  be  a  long 
round  bone.  It  really  consists  but  of  two  extremities.  Its 
superior  extremity  articulates  with  the  inferior  articulatory 
surface  of  os  suffraginis,  and  thus  presents  a  smooth  sur- 
face coated  with  articular  cartilage,  consisting  of  two 
shallow  concavities,  the  inner  of  which  is  the  largest. 
These  are  separated  by  a  slight  prominence,  extending  in  an 
antero-posterior  direction  ;  the  articulatory  surface  taken 
as  a  whole  is  concave  from  before  backwards,  and  the 
prominence  terminates  posteriorly  in  a  projecting  point. 
The  inferior  extremity  articulates  with  the  os  pedis  and  os 
naviculare ;  thus  it  presents  a  smooth  surface  which  is  broad 
jDOsteriorly,  and  at  the  anterior  part  terminates  in  a  point, 
to  which  the  coronal  process  of  the  os  pedis  is  adapted. 
The  surface  presents  two  prominences  separated  by  a 
shallow  groove ;  the  inner  division  is  slightly  the  largest. 
The  posterior  surface  of  the  bone  superiorly  presents  a  pro- 
minence extending  from  the  inner  to  the  outer  surface, 
which  superiorly  is  roughened  for  attachment  of  the  long 
inferior  sesamoideal  ligament,  and  below  this  presents  a 
smooth  surface  coated  with  articular  cartilage,  lubricated 
with  synovia,  over  which  the  flexor  pedis  perforans  plays 
immediately  after  passing  between  the  two  terminal  divi- 


282  OUTLINES    OF    EQUINE   ANATOMY. 

sions  of  perforatus,  wliich  become  attaclied  to  tlie  extre- 
mities of  this  ridge  inclined  to  the  lateral  surfaces  of  the 
bone.  Between  this  ridge  and  the  inferior  articulatory 
surface  the  posterior  part  of  the  bone  is  unoccupied,  merely 
presenting  foramina  for  the  passage  of  vessels  into  the 
bone.  The  lateral  surfaces  are  exactly  similar.  Superiorly 
they  are  roughened  for  attachment  of  the  broad  lateral 
ligament  of  the  pastern-joint.  Inferiorly,  inclined  to  the 
anterior  surface,  is  a  peculiar  depression,  which,  with  its 
fellow,  seems  as  though  the  bone,  when  in  a  soft  state,  had 
been  compressed  between  the  thumb  and  finger.  To  this 
the  lateral  ligament  of  the  pedal  joint  runs.  The  anterior 
surface  of  this  bone  is  occupied  by  the  expanded  inferior 
part  of  extensor  pedis  tendon,  which  is  attached  somewhat 
firmly  by  areolar  tissue. 

OS  PEDIS  is  an  irregular  bone,  and  since  it  receives  no 
bony  support  from  below  is  a  floating  bone.  It  is  sym- 
metrical, presenting  two  very  similar  halves,  the  inner  of 
which  is  the  smallest.  At  the  extreme  antero- inferior  part 
may  bo  seen  in  many  cases  a  notch,  a  trace  of  the  division, 
such  as  we  see  in  ruminants,  of  this  bone  into  two  similar 
parts.  It  presents  three  surfaces  :  supero-posterior,  infero- 
posterior,  and  antero-lateral.  The  supero-posterior  surface 
centrally  is  articulatory,  presentmg  a  surface  covered  with 
cartilage,  divided  primarily  into  two  parts.  The  anterior 
part  is  roughly  heart-shaped,  concave  in  an  antero-posterior 
direction,  elongated  and  slightly  convex  from  side  to  side. 
Anteriorly  it  terminates  in  an  obtuse  point,  extending  in 
an  upward  direction  on  the  posterior  surface  of  the  coronal 
process  ;  posteriorly  it  presents  an  oblique  angled  indenta- 
tion, into  which  the  posterior  part  fits.  The  sides  of  the 
oblique  angle  meet  the  external  convex  margins  of  the 
articulatory  surface  at  an  acute  angle  outwardly  and  pos- 
teriorly. This  surface  centrally  presents  an  antero-poste- 
rior broad  ridge  with  a  shallow  concavity  on  either  side, 
the  inner  being  slightly  the  largest.  It  articulates  ante- 
riorly with  OS  coronse,  and  this  portion  is  directly  continuous 
with  that  between  its  posterior  margins,  with  which  os 
naviculare  comes  in  apposition,  and  which  is  bounded  pos- 
teriorly by  a  line  extending  from  one  posterior  angle  of  the 
heart-shaped  surface  to  the  other.  This  surface  of  the 
bone  is  completed  by  a  roughened  ridge  on  each  side  run- 
ning at  first  outwards  and  then  directly  backwards  for 


THE    FOOT.  283 

about  three  eiglitlis  of  an  inch,  from  the  posterior  angles 
of  the  articulatory  surfaces.  The  point  where  the  ridges 
bend  backwards  form  posteriorly  smooth  grooves,  through 
which  the  plantar  arteries  run  downwards  in  their  course 
between  the  inferior  broad  ligament  of  the  navicular  bone 
and  the  perforaus  tendon  to  the  foramen  on  the  infero- 
posterior  surface  of  os  pedis. 

The  postero-inferior  surface  of  the  bone  is  mainly  occu- 
pied by  the  plantar  surface,  semilunar  in  form,  bounded 
by  two  margins,  which  meet  posteriorly  at  acute  angles. 
Thus  this  surface  is  broadest  centrally,  and  gradually 
decreases  in  size  posteriorly.  It  presents  a  slant  from  the 
greater  or  outer  to  the  lesser  or  inner  curved  margin,  and 
is  perforated  by  foramina,  which  are  most  numerous  at 
the  angles  and  at  the  outer  circumferent  margin ;  and  at 
the  line  of  junction  of  this  with  the  antero-lateral  surface 
is  a  series  of  openings  larger  than  the  rest.  Extending 
backwards  from  the  posterior  margin  is  a  roughened  space, 
bounded  posteriorly  by  the  articulatory  surface  for  os 
naviculare,  which  on  either  side  extends  slightly  on  to  this 
face  of  the  bone.  This  roughened  space  is  divided  on 
either  side  into  two  parts  by  a  groove  extending  from 
behind  forwards,  to  terminate  in  a  foramen.  Through 
this  the  terminal  portion  of  the  plantar  artery  runs,  and 
thus  gains  a  canal  extending  through  the  substance  of  the 
hone  from  one  foramen  to  the  other,  in  which  it  anasto- 
moses with  its  fellow,  completing  the  circulus  anteriosus 
of  the  foot.  The  walls  of  the  grooves,  as  well  as  those 
of  the  canal,  are  perforated  by  foramina,  through  which 
branches  pass  outwards.  The  space  between  these  grooves 
and  the  navicular  articulatory  surface  is  roughened  for 
attachment  of  the  inferior  broad  navicular  ligament ;  it 
is  perforated  by  articular  foramina.  That  space  between 
the  grooves  and  the  posterior  margin  of  the  plantar  sur- 
face is  about  three  eighths  of  an  inch  broad  in  the  centre, 
and  is  rough  for  attachment  of  the  extensor  pedis  tendon. 
The  antero-lateral  surface  is  largest  centrally,  and  gra- 
dually diminishes  in  size  posteriorly.  At  its  superior  part 
it  presents  a  smoother  portion  of  bone  than  the  rest,  of  a 
pyramidal  shape,  having  its  apex  superiorly  placed.  This 
is  the  coronal  process ;  around  its  superior  part,  at  about 
a  quarter  of  an  inch  from  its  superior  margin,  runs  a  line 
marking   out  the  inferior  attachment  of  extensor  pedis, 


284:  OUTLINES    OF    EQUINE    ANATOMY. 

■wliicli  tlius  intervenes  between  the  coronary  secreting  sub- 
stance and  the  bone  at  this  part.  This  surface  is  perforated 
by  numerous  foramina,  and  presents  small  irregular  plates 
running  from  above,  most  marked  near  the  inferior  mar- 
gin, where,  also,  at  varying  distances  from  each  other,  are 
large  foramina  for  the  passage  of  the  anterior  branches  of 
the  interosseous  plantar  artery,  which  assist  to  form  the 
circumflex  artery  of  the  toe.  Supero-laterally  is  a  deep 
depression,  smooth  at  its  bottom  for  attachment  of  the 
lateral  ligament  of  the  coffin-joint.  Behind  this  is  the 
alct,  running  backwards  for  attachment  of  the  lateral  car- 
tilage, which  also  seems  to  continue  the  bone  from  the  pos- 
terior margin  of  this  surface,  assisting  to  form  a  foramen 
through  which  the  lateral  laminal  branch  of  the  plantar 
artery  runs,  coursing  its  way  through  a  groove  in  a  forward 
direction  between  the  bone  and  the  sensitive  laminse  ;  at 
the  anterior  extremity  of  the  bone  it  enters  its  substance 
through  a  large  foramen.  It  sends  off  numerous  branches, 
especially  one  running  straight  downwards,  for  which 
there  is  a  special  secondary  groove,  and  which  forms  the 
commencement  of  the  circumflex  artery  of  the  toe.  The 
posterior  margin  of  this  surface  presents  superiorly  the 
ala,  inferiorly  the  angles  of  the  plantar  surface  ;  between 
these  two  is  the  lateral  laminal  groove.  They  are  rough, 
and  are  directly  continuous  with  the  lateral  cartilage.  In 
consequence  of  its  porous  nature,  and  the  close  reticula- 
tion of  blood-vessels  in  its  substance,  os  pedis  seems  to  be 
soft,  but  its  structure  in  the  dried  bone  will  be  found  to 
be  remarkably  hard. 

Attached  to  the  upper  margin  of  the  alae  of  os  pedis, 
extending  superiorly  for  about  one  and  a  half  inches, 
posteriorly  for  about  one  and  a  half  inches  behind  the 
posterior  extremities  of  the  alse,  and  extending  farthest 
forward  at  the  superior  part  of  their  anterior  margin, 
are  the  lateral  cartilag^es  of  the  foot.  These  are  pecu- 
liar shaped  portions  of  cartilage  which  present  two  sur- 
faces, three  margins.  The  external  surface  is  convex, 
extending  at  first  upwards  from  the  wing  of  os  pedis  with 
an  outward  inclination,  which  is  increased  along  its  pos- 
terior margin.  Its  anterior  extremity  becomes  ultimately 
blended  with  the  dense  fibrous  tissue  which,  in  this  situa- 
tion, seems  to  closely  unite  the  lateral  ligament  of  the 
pedal-joint  with  the  extensor  pedis  tendon  at  its  inferior 


THE    FOOT.  285 

extremity.  Posteriorly  tliis  surface  terminates  in  a  point 
at  about  one  and  a  half  inches  from  the  ala  of  os  pedis,  for 
here  the  cartilage  is  inflected  in  a  forward  direction,  form- 
ing that  portion  of  the  cartilage  which,  running  along  the 
inner  surface  of  the  wing  of  os  pedis,  gradually  terminates 
in  blending  with  the  white  fibrous  tissue  joining  the  ex- 
panded perforans  tendon.  Inwardly  it  is  continued  as  a, 
firm  but  fine  layer  of  fibrous  tissue,  which  serves  to  separate 
the  fibrous  frog  from  the  tendon.  The  inferior  margin  of 
the  cartilage  in  becoming  attached  to  the  bone  helps  to 
form  the  foramen  through  which  the  lateral  laminal  artery 
passes,  and  posteriorly,  on  its  under  surface,  presents  a 
triangular  continuation  of  the  plantar  surface  of  the  bone 
which  affords  attachment  to  the  sensitive  bars.^  The  m- 
ternal  surface,  as  a  whole,  is  concave,  and  looks  in  a  direc- 
tion inwards  and  slightly  upwards.  Its  inferior  part  is 
formed  by  the  upper  surface  of  the  inflections  of  the  carti- 
lages, which  here  are  closely  united  to  the  fibrous  frog^ 
many  of  the  elastic  fibres  of  which  become  attached  to  it. 
This  organ  is  separated  from  the  main  portion  of  _  thia 
surface  by  a  plexus  of  veins,  which  communicates  with  a 
corresponding  plexus  on  the  external  surface,  not  only  by 
branches  proceeding  ^through  numerous  foramina  in  the 
cartilage,  but  also  by  junction  of  their  resulting  vessels 
above  the  cartilage.  The  superior  margin  of  the  cartilage 
is  about  its  thinnest  part ;  the  thickest  is  that  just 
behind  os  pedis.  In  contact  with  the  plexus  of  vessels  on 
the  external  surface,  centrally,  hes  the  coronary  secreting 
substance,  superiorly  skin,  interiorly  the  upper  portions  of 
the  lateral  laminae,  which  are  supplied  by  a  special  branch 
detached  from  the  lateral  laminal  artery  running  back- 

wards. 

OS  NAVICTJLARE    (SHUTTLE   BONE)  is  a  sesamoid 

bone  situated  behind  and  slightly  resting  upon  os  pedis. 
It  is  elongated  from  side  to  side,  and  presents  two  sur- 
faces, two  margins,  and  two  extremities.  The  superior 
margin  looks  upwards  and  backwards ;  it  is  straight,  and 
presents  some  articular  foramina.  To  it  is  attached  the 
superior  broad  navicular  ligament,  which  runs  obliquely 
upwards  and  backwards  to  blend  with  \he  perforans  tQi\d.on, 
and  with  the  superior  band  of  the  stellate  ligament.  At  its 
posterior  edge  a  continuation  of  the  posterior  smooth  sur- 
face of  the  bone  is  visible.    Thi^  posterior  surface  is  covered 


286  OUTLINES    OF    EQUINE   ANATOMY. 

with  fibro- cartilage,  fonning  the  anterior  boundary  of  the 
navicular  joint,  and  affording  the  perforans  tendon  a  sur- 
face to  play  over.  Its  superior  margin  is  straight,  its 
inferior  convex.  It  presents  two  level  surfaces  sloping 
slightly  towards  the  centre,  and  thus  rendering  more  pro- 
minent a  ridge  which  here  extends  from  above  downwards 
across  the  surface.  The  inferior  margin  of  the  bone  is 
convex,  and  posteriorly  is  rough,  with  numerous  foramina, 
affording  attachment  to  the  inferior  broad  ligament  (run- 
ning from  this  to  the  postero-inferior  surface  of  os  pedis)  ; 
anteriorly  it  presents  a  smooth  articulatory  surface,  elon- 
gated from  side  to  side,  which  moves  arthrodially  on  a 
corresponding  surface  of  os  pedis,  and  is  continuous  by 
a  smooth  rounded  edge  with  the  iqji^er  or  anterior  surface 
of  the  bone.  This  is  covered  with  articular  cartilage, 
articulating  with  os  coronae  ;  it  has  two  elongated  concave 
surfaces,  which  centrally  are  separated  by  a  broad  con- 
vexity. Its  superior  margin  is  straight,  its  inferior  convex. 
The  surfaces  and  margins  culminate  in  the  two  extremities, 
which  are  angles,  with  a  slight  inclination  in  a  posterior 
direction.  To  them  are  attached  the  stellate  navicular 
ligaments,  each  of  which,  attached  here  by  a  single  head, 
divides  into  three  parts,  one  of  which  runs  to  the  inner 
part  of  the  wing  of  os  pedis,  blending  with  the  inferior 
broad  ligament,  another  runs  to  inner  surface  of  the  lateral 
cartilage,  while  the  third,  after  uniting  with  the  terminal 
expansion  of  the  perforans  tendon,  passes  upwards  and 
divides,  one  part,  after  becoming  attached  to  the  inner 
surface  of  the  sujjerior  part  of  the  lateral  cartilage  being 
continued  on  to  blend  with  the  lateral  ligament  of  the 
pastern- joint,  while  the  other  runs  direct  to  the  middle 
of  the  lateral  surface  of  os  suffraginis,  where  it  is 
attached. 

We  have  now  examined  the  articulatory  surfaces  which 
enter  into  the  formation  of  the  coffin  and  navicular  joints. 
The  synovial  membrane  of  the  former  covers  the  inner 
surface  of  part  of  extensor  pedis  tendon  and  of  the  lateral 
ligaments,  and  covers  the  anterior  surface  of  both  the  broad 
navicular  ligaments.  We  have  here  a  peculiar,  but  not 
exceptional,  union  of  a  ginglymoid  with  an  arthrodial 
joint.  The  arrangement  of  the  tendinous  structure  around 
prevents  the  necessity  for  a  capsular  ligament.  The  syno- 
vial membrane  of  the  navicular  joint  (or  more  correctly 


THE    FOOT.  287 

bursa),  after  covering  tlie  antero-superior  part  of  the  iiife- 
rior  jDortion  of  the  tendon  on  reaching  the  superior  broad 
ligament  above,  is  reflected  over  its  posterior  surface  as 
far  as  the  bone,  while  from  below  it  is  reflected  upwards 
over  the  posterior  surface  of  the  inferior  broad  ligament 
centrally,  and  laterally  comes  in  contact  with  the  stellate 
ligament. 

The  blood-vessels  and  nerves  of  the  foot  have  been  already 
noticed,  but  we  may  here  repeat  that  each  metacarpal  or 
metatarsal  nerve  just  above  the  fetlock  breaks  up  into 
three  divisions,  which  pass  downwards  over  the  lateral 
surface  of  the  joint,  in  company  with  the  plantar  vein  and 
artery.  The  anterior  division  runs  forwards  to  suj^ply  the 
structures  in  front  of  the  joint. 

The  middle  division  or  anterior  plantar  nerve,  crossing 
the  artery  from  behind  forwards,  runs  to  the  coronet, 
during  the  first  part  of  its  course  situated  behind  the 
artery  and  vein. 

The  posterior  division  or  posterior  plantar  nerve  is 
situated  behind  the  artery,  and  accompanies  it  to  the  pos- 
terior part  of  the  foot,  sending  off  fibres  to  accompany 
many  of  its  branches  ;  this  nerve  is  divided  in  the  "  Zo^y  " 
operation  of  neurotomy.  The  inferior  extremity  of  the 
metacarpal  nerve  before  division  is  involved  in  the  "  high" 
operation. 

The  flexor  tendons  must  now  be  examined. 

While  passing  through  the  sesamoid  groove  at  the  back 
of  the  fetlock  the  perforatus  tendon  extends  round  the  per- 
forans,  and  thus  forms  a  sheath  for  it,  which  is  deficient 
anteriorly,  so  that  the  theca  between  the  tendons  com- 
municates with  the  sesamoid  bursa.  From  the  supero- 
lateral angles  of  os  suffraginis  portions  of  white  fibrous 
tissue  run  to  the  posterior  surface  of  the  perforatus  tendon, 
which  shortly  after  bifurcates  one  of  its  divisions  runnino- 
to  each  extremity  of  the  posterior  fibro-cartilaginous  sur- 
face of  OS  coronge.  Between  the  divisions  the  perforans 
tendon  runs,  playing  over  the  fibro-cartilaginous  surface  ; 
to  its  posterior  surface  run  white  fibrous  tissue  layers  from 
the  infero-lateral  parts  of  os  suffraginis  ;  thus  reinforced  it 
receives  some  white  and  yellow  elastic  fibres  from  the 
superior  margin  of  the  navicular  bone  (superior  broad 
ligament)  which  run  to  its  anterior  surface.  It  then  plays 
over  the  inferior  surface  of   os   naviculare,  through  the 


288  OUTLINES    OF    EQUINE    ANATOMY. 

medium  of  the  navicular  bursa,  and  becomes  inserted  by  a 
wide  attachment  to  the  posterior  margin  of  the  plantar 
surface  of  os  pedis.  Its  under  surface  is  separated  from 
the  fibrous  frog  by  a  white  fibrous  layer,  which  connects 
the  lateral  cartilages  at  their  inferior  inflections. 


nary  (Right  and  Left)  200 
rBBioR  f  Arteriaj  Inno- 
194   *        I  (right'SntTleft^ 


ARTERIAL    TREE. 

Posterior  corvicnl— let  intcrcoBtoI,  179  antl  1S5 
Aoterior  dorsal  j  2nd  intercostal,  1"' 
186  Isubcostal— 3rd,  4 

Vertebral  178 

Carotid  (common)  f  Bight    I  Ramus  anastomoticus 


Sy)  19' 


i8  <Occipital  168 
Posterior  communicating  161 
i  &   I  Internal  carotid  168     ■(  Middle  cerebral  161 
78     I                                          ^Anterior  communicating  161 
I  Tbj-roidcal  178— Laryngeal  178 
l^Eiternal  carotid  168    f  Submaxillary  .  .  Lingual  |  Ranine 


i.  Ophthalm 


bmaxillary  . 
117  and  169 


I  Branch  to  thymus  gland  184 

Anterior  abdomimil  194 
I^Superior  branch  194 


Sublingual  1 
Submental  or  myeloid 
Inferior  labial  117 
Anterior  masseteric  11 
Superior  labial  117  — 


Axillary    j  External  thoracic 
206  Humeral  thoracic  zuo 

Anterior  scapular  (art.  dorsalis  scapula-)  206     .r. .,,.,., 

I  Posterior  scapular  or  subscapular  203 i  Medulla: 

LHumeral  206  | 


1  I  Branch  to  Hex 
Medullary  of  I 
I  Muscular  brar 


^loQ 


liar  (sometimes)  123 

Inferior  maxillary  

Deep  temporal  branches  125 

Ocular  I  Supra-orbital  126 

Ciliary  126 

l_  Lateral 


fMolar  branches  125 


branches  to  sup.  meatus  126 

--■-"'       iddle  meatus  126 

iferior  meatus  126 

'  .  ralatine 

I  Molar  branches  126 
Canine  branches  126 
Incisor  branches  126 
tlnfra-orbilal  branches  126 


Branch  t' 
Superficial  coronary  i  . 
Deep-seated  coronary  J 
Branch  to  frog  I  Branch 


ARTERIAL  T'REE—ouiiUiiu 


b189 
I  supbiior  branches  238 
Lumbar  {  Inferior  branches  238 


Medullary  of  dorsal  vertebra  180 
Branch  to  spinal  cord  and  its  mem 
Dorsal  branches  187 
1  Cutaneous,  muscular,  and  pleural  b 


Medullary  of  lumbar  verlebrs  238 
i  Branches  to  spinal  cordaudit8membranes238 

rGastric  <  Superior  237 "| 

sis  i      237    5  Inferior  237 }-~^ 

Splenic  237    .    Left  gastric  237- J       "-^ ^ 

[Hepatic  226   f  Branches  to  the  liver  226  ' 

}  Duodenal  branch  226  r  Eight  giistric  2-. 

f  Pancreatic  237  i  Intestinal  226 

Duodenal  237 
Mesenteric  (15-18  in  number)  237 


237    t  Branches  i 


I  Branch  t 
)rL-renal  capei 
)  kidney  237 


237   fTwo  branches  to  double  colol 

(.Branch  to  single  colon  237 
ich  to  single  colon  237 


237 


Branches  to  spermatic  cord  237 
Branches  to  epididymis  237 
Artery  of  cord  (male)  263  ,  Sometimes  from  external  iliac 


:  i  Artery  of  tl 


■  Middle  coccygeal  (sometimes)  26.5 
fUmbilical    {|:-f,'ES261 
Vesical  branches  2(U 

1  and  perineal  branches  2Gi 


1  Cutaacoua  braucbee  '270 


the  bladder  2(31 


Auterioi-  tibial 


/Large  meta 
1  271 


^  riantars  1 
13  branches  271 
:  branches  271 


|.r; 


Obturator     <  Pubic  264 
26-1  Ischiatic  264 

[^ Internal  pubic  —  Posterior  dorsal  artery  of  the  penia  264 
Gluteal  265  ,  ^^^ 

Lateral  sacral  265  —  Lateral  (sometimes  middle)  coccygeal  265 
C Circumflex  artery  of  the  ilium  262 
(  Arteria  profunda  ("Epigastr-   ''"—^ 

of  penis  2G3 


rPost.  abdominal  branches  263 
Externiil  pudicf  Anterior  dorsal  artery 
(.  -        ■    — " 


NEKVOUS  SYSTEM. 


Sympatlietic  Bystem  13 


ilhmuB  h:jo  uemispnfres 

I  Cnghtanikft)] 

Ifactory  bulb  and  sheath  160 


Hcmiapheres  lol 
Superior  tracts  181 


aiuus  opticus    f"  Corpora  geniculal 
157  <  Tubercle  1=" 

Grey  com. 


fimbriate  1 
Septum  lucidum  1 
[Corpus  albicans  16 


Crura     f  Anterior  (processus  ad 
159    J.  testes)  153 

Middle  (pons  Varolii) 
1.59 
(.Posterior  160 


Corpora  py 

Corpora  pyramida-    Inferior  ditto 

Ha  inf.  160 
Corp. 

Corp. 


On    the  superior    Cervical  superior  179    Card 


Pharjnge«l  177 
Pulmonary  192 
Cardiac  2O0 


Posterior  mesenteric 


Vertebral  195 
Gangliated  cord  19.5 
Splflichnic  greater  19- 
„         leaser  195 
CUiary  145 
Inhibitory  [?]  (with 


H^gas 


Corpora  quadrigemiaa  <  Testes  lo8 
'ineal  body  and  its  crura  158 


Complex 
isso-pharj'Dgeal  f  Glossal  branch  (f 

9th,  139  I  Pharyngeal 

r Communicating  branchea  177 
eumogastric  < 

10th,  177       Superior  laryngeal 


lea  177 
Pharyngeal  177 


Portio  molli8,8th,  164 


Inferior  laryngeal  or  recurrent  177 
Branches  to  thoracic  plexus  192 
„         ganglia  192 
CEsophageal      (-Gastric  branches 
(sup.  and  inf.)  tBraneh  to  solar  ple3 
Sensory    fOphthal-  T  Palpebral 


Pathetic  or  trochlear,  4 
dbduccns,  6th,  145 
Spinal  accessory,  11th, 
Lingual,  12th,  136 


f  opbthalti 
Tympani. 


Petrosal        facial 


Superior 
lary  127 


halniic  ganglio 
'  Branch  to  molar 


Pal  a  to- max  i  I 
J.  dental  1 
Molar 


r  Branches  to  sup.  cer- 
vical ganglion 
Auricular  branches 
Branches   to    neigh- 
bouring nerves 

[         Ac. 


Istto  17lh  or  18th 
Muscular  branches  &c. 
Branches  to  gangliated  cord 
Intercostal  branches 


Lumbar  265 
Ist  Muscular  superior 

Ganglionic 
Abdominal 

crural  fibres 
3rd  1  Similar  to  2nd  a 


Ganglionic  fibres 
Gluteal  fibres 

Sciatic  fibres 

Muscular  superior 
„        inferior 


Infra-orbital  branch 
Inferior  f  Facial  branch  119 
maxil-   <   Buccal  branch 
lary  124       Auricular  branch  124 

Gustatory  branch  124  (special  seuse) 
[^  Inferior  dental 


i  5th  muscular  and  phrenic  branchea 
i  8th  muscular  branchea  and  axillary 
1  and  communicating   branches   to 


Subscapular 
Humeral  thoracic 
External  thoracic 
Muscular  branches 


3rd    Muscular  super: 
„       inferii 
Coccygeal 
Ganglionic 

4lh— Coccygeal  &c. 


bmral 

Ulnar — External  metararpal  r  Plantar  r 

Radial— Internal  mclaoarpan         '  .,;» 


^Popliteal  267 

;  Anterior  tibial  267 

1^  Posterior  tibial  272 

Ext.  metatarsal  21 

Int.  metatarsal  27 


INDEX. 

PACK 

PAGE 

^Abdomen 

.  216 

Angle  of  inferior  maxilla 

.     41 

—  divisions  of 

.  231 

—  mouth     . 

.  120 

—  lining  membrane  of 

.  222 

—  palpebral  fissure 

.  120 

—  muscles  of 

.  220 

—  rib  . 

.     58 

—  regions  of 

.  231 

Ankle  .... 

.     92 

■ —  viscera  of 

.  224 

Annular  cartilage 

.  122 

Abdominal  rings  . 

.  219 

—  ligaments 

.     11 

Absorbent  glands,  see  Glands 

Annulus  ovalis 

.  197 

lymphatic. 

Anthropotomy 

.       1 

Absorbents,  see  Lymphatics. 

Antrum 

.  142 

Acetabulum . 

.     82 

Anus     .... 

.  235 

Acini    .... 

.  226 

Aorta    .... 

.  199 

Afferent  lymphatics 

.     19 

—  anterior  . 

.  194 

—  vessel  of  kidney 

.  240 

—  posterior 

.  236 

Age  of  subject  for  dissection 

3 

—  valves  of 

.  199 

—  as  shown  by  teeth    . 

.  131 

Apophysis     . 

.       8 

Air  cells 

.  191 

Apparatus,  lachrymal    . 

.  121 

—  sacs 

.  192 

Appendix 

.  197 

Alse  of  atlas 

.    48 

Aqueduct  of  Sylvius 

.  158 

—  nostrils     . 

.  139 

Aqueous  humour 

.  149 

—  thyroid  cartilage 

173 

Arachnoid  (cranial) 

.  154 

Albuginea  testis,  tunica 

246 

—  fluid 

.  155 

Allantois 

255 

—  (spinal)    . 

.  180 

Allantoid  sac 

255 

Arch,  crural 

.  219 

Alveoli 

34 

—  haemal      . 

.     42 

Amnion 

255 

—  fibular     . 

.     92 

Amphiarthrosis     . 

100 

—  ischial      . 

.     85 

Ampullae 

163 

—  neural 

.     42 

Anastomosis  (of  arteries) 

21 

—  palatine 

.     38 

Anatomy 

1 

—  radio-ulnar 

.     69 

—  comparative     . 

1 

—  vertebral 

.     43 

—  descriptive 

2 

—  zygomatic,  5ee  Zygomatic  ridge. 

—  general    . 

1 

Arcus  senilis 

.  147 

—  pathological     . 

2 

Arteries,  general  description 

—  philosophical    . 

2 

of          .         .         . 

.     20 

—  transcendental 

1 

—  injection  of 

.       2 

39 


290 


INDEX. 


PAGK 

PAGE 

Arteries,  coats  of 

.     21 

Arteries,  iliac,  internal 

.  264 

—  descriptive  anatomy  of: 

—  infra-orbital,  see  Superior 

—  abdominal 

.  221 

dental. 

—  aorta 

.  199 

—  inguinal  . 

.  263 

—     —  anterior    . 

.  194 

—  innominate,  right 

.  194 

—     —  posterior  . 

.  236 

—     —  left  . 

.  194 

—  auricular 

.  123 

—     —  branch  of  obtu 

i-ator.  264 

—  axillary 

.  206 

—  intercostals 

185,  186 

—  basilar     . 

.  161 

—     —  first 

.  179 

—  bronchial 

.  192 

—  ischiatic  . 

.  264 

—  of  bulb    . 

■       .  26i 

—  labial,  superior 

.  117 

—  carotid,  common,  16 

3,178,194 

—  lachrymal 

.  145 

—     —  external  . 

.  168 

—  laminal,  lateral 

.  214 

—     —  internal    . 

.  168 

—  laryngeal 

.  178 

—  centralis  retinae 

.  145 

—  lingual     . 

.  136 

—  cerebellal 

.  161 

—  lumbar    . 

.  238 

—  cerebral  . 

.  161 

—  mammary 

.  263 

—  cervical,  inferior 

.  179 

—  masseteric 

.  117 

■ —  "  —  posterior  . 

179,  185 

—  maxilary,  internal 

.  125 

—  ciliary 

.  145 

—     —  inferior     . 

.  125 

—  circulus  arteriosus  p 

edis  .  214 

—  mesenteric 

.  227 

—  circumflex,  of  ilium 

.  262 

—     —  anterior    . 

.  237 

—  toe           .         . 

.  215 

—     —  posterior  . 

.  237 

—  coccygeal 

.  265 

—  metacarpal,  small 

.  213 

—  cceliac      . 

.  237 

—     —  large 

.  214 

—  csecal 

.  237 

—  metatarsal,  large 

.  271 

—  colic 

.  237 

—     —  recurrent 

.  271 

—  communicating 

.  161 

—  nasal,  lateral  . 

.  126 

—  of  cord    . 

,  263 

—  obturator 

.  264 

—  coronary,  of  heart 

.  200 

—  occipital 

.  168 

—     —  foJt 

.  214 

—  oesophageal 

.  192 

—  corporis  callosi 

.  156 

—  ophthalmic 

.  145 

—  dental,  superior 

.  126 

—  orbital     . 

.  145 

—  dorsal      . 

.  185 

—  ovarian    . 

.  238 

—  dorsalis  scapulae 

.  217 

—  palato-mixillary 

.  126 

—  diaphragmatic,  see  ] 

Phrenic. 

—  pectoral,  external,  se 

eTho- 

—  duodenal  of  hepatic 

.  226 

racic. 

—  emnlgent 

.  237 

—  phrenic  . 

.  189 

—  epigastric 

.  263 

—  plantar    . 

.  214 

—  facial 

.  117 

—  profunda  femoris 

.  263 

—  femoral   . 

,  263 

—  pubic 

.  264 

—  of  frog    . 

.  214 

—  pudic,  external 

.  263 

—  gastric,  superior 

.  231 

—     —  internal    . 

.  264 

—     —  inferior    . 

.  231 

—  pulmonary 

.  198 

—     —  right 

.  231 

—  radial 

.  206 

—     —  left  . 

.  231 

—  ramus  anastomoticu 

3        .  168 

—  gluteal    . 

.  265 

—  ranine 

.  136 

—  hepatic    . 

.  226 

—  recurrent 

.  270 

—  humeral  . 

.  206 

—  renal 

.  237 

thoracic 

.  206 

—  sacral,  middle 

.  265 

—  iliac,  external 

.  262 

—     —  lateral       . 

.  265 

INDEX. 


291 


PAGE 
217 

217 
286 
238 
126 
200 
237 
236 
136 
169 
217 


Arteries,  scapular,    anterior 
206, 

—  —     —  posterior  .    206, 

—  solar 

—  spermatic 

—  spheno-palatine 

—  spiral 

—  "splenic     . 

—  of  stomach 

—  sublingual 
-7  submaxillary  .         .    I17. 

—  subscapular      . 

—  subzygomatic,    see   Tem- 

poral. 

—  supra-orbital  .         .  .   126 

—  temporal  .         .         ,  igg 

—  —  deep  .         .         .  125 

—  thoracic,  external     .         .  2IS 

—  —  internal  .  .  .  194 
— ■  thyroid    .         .         .         .178 

—  tibial,  anterior         .  .  270 

—  —  posterior  .         .  270 

—  ■ulnar       ....  206 

—  umbilical  .  .  .  264 
--  uterine    .         .  238,  263 

—  utero-ovarian,  see  Ovarian. 

—  vertebral  .         .         .  173 

—  vesico-prostatic  .  .  264< 
Arthrodial  joint  .  .  .  100 
Arthrology  ....  199 
Articular  cartilage         .         .17 

—  eminences        ...       9 

—  laminae    .         .         .         .10 
Articulation,  see  Joint. 
Arytenoid  cartilages      .         .  172 
Ass       .....       3 
Auditory  canal,  external        .  123 

—  meatus,  external      .         .123 

—  —  internal  .  .  .32 
Auricle  of  heart,  right  .         .  197 

—  left  .  .  .  .199 
Auriculo- ventricular  furrows  196 

—  —  opening,  right  .  198 

—  —     —  left  .         .         .199 

—  —  valves  .  .  .199 
Axonoidal  joints  .  .  .  101 
Azygos  vena  .         .         .  187 


Bacillary  layer 
Back     . 
Barb     . 


148 
183 
132 


Bars  of  hoof 
Base  of  mouth 

—  brain 

Ba'^ement  membrane 
"  Beastlings  " 
Belly  of  muscle     . 
Bicuspid  valve 
Bile  duct 
Bladder,  gall,  absence  of 

—  urinary    . 

—  —  foetal 

—  —  ligaments 
Blind  spot    . 
Blood,  circulation  of. 

—  vessels     . 
Body  of  thyroid    . 
Bone,  general  anatomy 

—  cavities  of 

—  composition  of 

—  classes  of 

—  tissue,  kinds  of 

—  eminences  of  . 

—  formation  and  grow 

—  Haversian  canals 

—  —  systems    . 

—  lacunae  of 

—  lamellas  . 

—  medulla  of 

—  periosteum  of  . 

—  processes  of      . 

—  organization  of 

—  long,  round 

—  flat 

—  short 

—  irregular 

—  astragalus 

—  atlas 

—  axis 

—  oaleis 

—  carpal 

—  coccygeal  vertebras 

—  coronal    . 

—  cranial     . 

—  cuboid     . 

—  cuneiform  of  carpus 

—  —  magnum  (tarsus) 

—  —  medium 

—  —  parvum 

—  ear 

—  ethmoid 

—  face 


of 


thof 


FAOX 

.  276 
.  128 
.  160 
.  14 
.  232 
.  12 
.  199 
.  233 
.  225 
.  241 
.  255 
.  241 
.  148 

.  19 
.  166 

.  7 
.  10 
.  6 
.  8 
.  8 
10 
7 

.  8 
.  8 
.  8 
.  8 
.  8 
.  9 
.  10 
.  9 
.  8 
.  9 
.  9 
.  9 
.  93 
.  47 
.  49 
.  92 
.  72 
.  56 
.  281 
.  150 

.   m 

.  73 

.  94 

.  95 

.  96 

.  164 

.  29 

.  S3 


292 


INDEX. 


Bone,  femur 

PAGE 

.     85 

Bone,  sufFraginis  . 

—  fibula 

.     91 

—  tarsal 

—  foot 

.  281 

—  temporal,  petrous 

—  forearm  . 

.     68 

—     —  squamous 

—  fore  extremity 

.     61 

—  tibia 

—  frontal    . 

.    27 

—  trapezium 

—  hind  extremity 

.     82 

—  trapezoid 

—  hock 

.     92 

—  triquatral 

—  humerus 

.     65 

—  turbinated,  superior 

—  hyoid 

.  133 

—     —  inferior     . 

—  ilium 

.     82 

—  ulna 

—  incus 

.  164 

—  unciform 

—  innominate 

.     82 

—  vertebral,  cervical 

—  ischium 

.     84 

—    —  coccygeal 

—  lachrymal 

.     36 

—     —  dorsal 

—  lunare      . 

.    72 

—     —  false 

—  magnum 

.        .    75 

—     —  lumbal      . 

—  malar 

.     38 

—     —  sacral 

■ —  malleus    . 

.  165 

—     —  true 

■ —  maxillary,  anterior 

.     33 

—     —  typical      . 

—     —  inferior     . 

.     40 

—  vomer 

—     —  superior   . 

.     34 

—     zygomatic 

—  metacarpal,  large 

.    77 

Brain    . 

—     —  small 

.    78 

circle  of  Willis 

—  metatarsal,  large 

.     98 

ventricles     . 

—     —  small  inner 

.     98 

Bronchi 

—     —     —  outer 

.     98 

B runner's  glands  . 

—  nasal 

.     33 

Buccal  salivary  glands 

—  navicular 

.  285 

Bulb,  olfactory     . 

—  occipital 

.     24 

—  penis 

—  palatine 

.        .    37 

—  vagina     . 

—  parietal  . 

.     26 

Bursa   . 

• —  patella     . 

.     88 

—  pedal  (fore)      . 

.  282 

Caecum 

—     —  (hind)       . 

.     98 

—  caput  coli 

—  pelvic 

.     82 

Calamus  scriptorius 

—  pisiform  . 

.    77 

Calcaneo-cuboid  ligame 

lit 

—  pterygoid 

.     38 

Calyces  of  kidney 

—  pubic 

.     85 

Canals  .... 

—  quadrate 

.  101 

CanaJ,    alimentary,   see    ^ 

— •  radius 

.     68 

mach,  &c. 

—  ribs 

.     56 

—  Haversian 

—  sacral 

.     54 

—  auditory  external     . 

—  scaphoid 

.     72 

—  of  Fontana 

—  scapula    . 

.     61 

—  of  Petit    . 

—  sesamoid 

80,  98 

—   inguinal . 

—  shuttle    . 

.  285 

—  spinal 

—  skull 

.     24 

Canaliculi     . 

—  sphenoid 

.     30 

Cancellated  structure    . 

—  stapes 

.  164 

Canine  teeth 

—  sternal    . 

.     60 

Cauthi  of  eyelids  . 

Sto- 


INDEX. 


293 


PAGE 

PAGE 

Capillaries    . 

.     26 

Cauda  equina 

.  266 

Capsular  ligaments        .         .  100 

Caudatus  lobus      . 

.  225 

Capsule,  Glisson's 

.  226 

Caul      . 

.  230 

—  of  lens     . 

.  149 

Cavernosum,  corpus 

.  243 

—  pre-renal 

.  236 

Cavernous  sinus    . 

.  154 

—  supra-renal,  see  Pre-renal  236 

Cavities  of  bones  . 

9,  10 

—  renal 

.  239 

—  heart. 

.  196 

Caput  gallinaginis 

.  242 

—  reserve    . 

.  130 

Cardia  of  stomacli 

.  229 

Cavity,  abdominal 

.  230 

Cardiac  ligament . 

.  224 

—  alveolar   . 

.     33 

Cariniform  cartila 

ge     .         .60 

—  cranial     , 

.  150 

CarneaB  columnse 

.  198 

—  glenoid    . 

.     63 

Carpus,  bones 

.    71 

—  pulp 

.  132 

—  articulations 

.  107 

Cells,  ethmoid 

.     30 

Cartilage 

.      7 

—  hepatic    . 

.  226 

General : 

—  mastoid  . 

.  164 

—  cellular    . 

.       8 

—  nerve 

.     14 

—  elastic      , 

.      7 

Cementum    . 

.  129 

—  fibro- 

.      7 

Centralis  retina  arteria 

.  145 

—  hyaline    . 

.      7 

Centrum  ovale  major 

.  156 

—  permanent 

.      7 

—     —  minor 

.  156 

—  temporary 

.       8 

—  vertebral 

.     43 

—  true 

.      7 

—  nerve 

.     13 

—  articular  . 

.7 

Cerebellum  . 

.  159 

Particular  : 

Cerebro-spinal   nervous 

sys- 

—  annular  . 

122 

tem 

.     13 

—  arytenoid 

*.  175 

Cerebrum 

.  155 

—  auricular 

.  122 

—  crura  of  . 

.  160 

—  cariniform 

.     60 

Ceruminous  glands 

.  123 

—  costal 

.     58 

Cervix    vesicae,  see  Neck  of 

—  cricoid     . 

.  174 

bladder. 

—  elongation  of  scapula       .     63 

—  uteri,  see  Neck  of  u' 

erus. 

—     —  ribs 

.     58 

Chambers  of  the  eye 

.  149 

—     —  ensiform 

.     60 

—  nasal 

.  139 

—  epiglottis 

.  174 

Channels 

.     10 

—  of  foot  (lateral)        .         .  284 

Cheek  . 

.  118 

—  inter-articular 

discs     of 

Chestnut 

.  208 

stifle-joint 

.  Ill 

Chorda  tympani    . 

.  124 

—     —  temporo  ■ 

maxillary 

Chordae  tendinese 

.  198 

joint 

.  101 

Chorion 

.  253 

—  larynx     . 

.  173 

Choroid 

.  147 

—  nictitans 

.  143 

—  plexus  of  lateral   ventri- 

— of  nostrils 

.  139 

cles 

.  155 

—  septum  nasi 

.  173 

—     —  of  third  ventri( 

jle      .  155 

—  scutiform 

.  122 

Cilise    . 

.     16 

—  tarsal 

.  120 

Ciliary  arteries 

.     16 

—  thyroid    . 

.  173 

—  ligament 

.  148 

—  of trachea 

.  176 

—  processes 

.  147 

—  xiphoid  . 

.     60 

—  zone 

.  149 

Curuncula  lachry 

malis          .  121 

Ciliated  epithelium 

.     16 

Carunculse  myrtif 

ormes         .  251 

Cineritious  brain  mattei 

r         .  156 

294 


INDEX. 


Circle  of  Willis     . 
Circulation,  blood,  foetal 
—  through  liver  . 
Circulus  arteriosus  pedis 


PAGE 

161 

253 

.  226 

,  214 


Circumferential  cartilage  (hip)  111 
Circumflex  artery  of  the  toe  215 


Clitoris 

.  251 

Coats  of  stomach 

.  230 

Coccyx          .       ' . 

.     56 

Coccygeal  vertebrae 

.     56 

Cochlea 

.  163 

Cceliac  axis  . 

.  237 

Colon,  double 

.  234 

—  single 

.  235 

Colostrum     . 

.  253 

Colour  of  the  hoof 

.  276 

Column,  vertebral 

.     42 

ColumnsB  carnese 

.  198 

Columns  of  spinal  cord 

.  181 

Commissures  of  hoof     . 

.  274 

—  grey 

.  157 

—  soft 

.  157 

—  of  spinal  cord  . 

.  181 

—  anterior  . 

.  158 

—  posterior 

.  158 

Communicating  arteries 

.  161 

—  foramina,  anterior  . 

.  158 

—     —  posterior  . 

.  158 

Compact  tissue  of  bone 

.       8 

Compound  glands 

.     19 

Conchial  cartilage 

.  122 

Condyles 

.     10 

—  of  femur 

.     88 

—  of  humerus      . 

.     67 

—  of  inferior  maxilla  . 

.     40 

—  of  occiput 

24,25 

Conjunctiva 

.  121 

Constrictors  of  the  pharynx 

.  138 

Contorti  tubuli     . 

.  240 

Convolutions  of  the  brain 

.  155 

Coracoid  process  . 

.     61 

Cord,  artery  of     . 

.  238 

—  sperm.atic 

.  245 

—  spinal 

.  180 

—  umbilical 

.  255 

Cord 03  vocales 

.  175 

—  Willisii  . 

.  153 

Corium 

.     16 

Cornea 

.     46 

Corneal  cartilage . 

.  139 

Cornua  of  os  hyoides,  short 

.  134 

Cornua  of  os  hyoides,  long 

—  of  spinal  cord . 

—  of  thyroid  cartilage 

—  of  ventricles  (lateral) 
Corona  glandis 

—  tubulorum 
Coronal  suture 
Coronary  arteries . 

—  fibrous  band    . 

—  frog  band 

—  secreting  substance 
Corpus  albicans    . 

—  callosum. 

—  cavernosum 

—  dentatum 

—  geniculatum    . 

—  luteum    .         .   • 

—  olivare    . 

—  spongiosum 
Corpora  arantii     . 

—  striatum . 

—  pyramidalia     . 

—  restiformia 

—  nigra 

—  quadrigemina . 
Corpuscles,    Malpighian, 

kidney  . 

—  -^  spleen 
Costse  . 

Costal  cartilages  . 
Cotyloid  cartilage 

—  cavity      . 
Cowper's  glands   . 
Cranium 
Cranial  nerves 
Cremasteric  faschia 
Crest    . 

—  of  occiput 

—  of  ilium  . 
Cribriform     plates     of     the 

ethmoid 
Cricoid  cartilage  . 
Crista  galli  process 
Crown  of  tooth  . 
Crucial  ligament  . 
Crura  cerebri 

—  cerebcUi . 

—  of  corpus  cavernosu 

—  of  diaphragm  . 

—  fornix 

—  of  pineal  body 


INDEX. 


295 


PAGE 

tAGE 

Crura  of  splienoid  bone 

.     31 

Dacts,  nasal 

.  143 

Crural  arch  ... 

.  219 

—  pancreatic 

.  224 

Crusta  petrosa 

.  129 

—  of  Stenson 

.  141 

Crypts,  mucous     . 

.  242 

—  thoracic  . 

.  195 

Crystalliue  lens    . 

.  148 

—  Wharton's 

.  132 

Curvatures  of  stomach 

.  229 

—  ejaculatory 

.  247 

—  spleen      . 

.  236 

Ductus  ad  nasum . 

.  143 

Cuticle,  see' Epidermis. 

—  arteriosus 

.   198,254 

Cuticular  layer  of"  stomach   .  230 

—  venosus    . 

.  253 

Cutting  the  teeth 

.  130 

Ductless  glands    . 

.     19 

Cylinder,  axis 

.     14 

Duodenum   . 

.  233 

Dura  mater  of  the  bra 

in        .  153 

Dark  chamber 

.  149 

—     —  cord 

.  180 

Decidua  membrana 

.  250 

Decussation,  optic 

.  160 

Ear       . 

.  163 

—  of  motor  fibres 

.  160 

—  external  . 

.  122 

Dentata 

.     49 

—  internal  . 

.  163 

Dentition  (table)  . 

.  131 

—  middle    . 

.  164 

Dentine 

.  129 

—  wax,  see  Cerumen. 

Depressions    on    bones 

,    see 

Ejaculatory  ducts 

.  247 

Cavities. 

Elastic  tissue 

.      7 

Dermis 

.    17 

Elastica,  cornea    . 

.  146 

Descent  of  testis  . 

.  246 

Elongation,  cartilage, 

of  rib .     58 

Destruction  of  subject 

.       4 

—     —  of  scapula 

.     62 

Detrusor  urinae     . 

.  242 

Eminences  of  bones 

.      9 

Development  of  teeth  . 

.  130 

Enamel 

.  129 

Diaphragm  . 

.  188 

Encephalon  . 

.  162 

Diapophysis . 

.       8 

Endocardium 

.  196 

Diarthrosis  . 

.  100 

Endolymph 

.  163 

Digital  impressions 

.     10 

Ensiform  cartilage 

.     60 

Digastric  muscles 

.     12 

Epidermis     . 

.  434 

Digestive    organs,   see 

Stomach, 

Epididymis  . 

.  247 

&c. 

Epiglottis     . 

.  289 

Dilators  of  the  pharyn 

X        .  138 

Epiphysis      . 

.       8 

Diploe 

9,150 

Epithelium,  ciliated 

.     16 

Disc,  optic    . 

.  148 

—  columnar 

.     16 

Dissection  of  head 

.  115 

—  spheroidal 

.     16 

—  of  neck  . 

.  166 

—  stratified 

.     16 

—  of  abdomen      . 

.  216 

—  tesselated 

.     15 

—  of  back    . 

.  183 

Erectile  tissue 

.  236 

—  of  fore  extremity 

.  201 

Ethmoid  bone 

.     29 

—  of  hind  extremity 

.  257 

—  cells 

.     30 

Division  of  the  subject 

.       4 

—  fosso3 

.  151 

Dorsal  vertebrae    . 

.     50 

—  sinuses     . 

.     29,  142 

Dorsum  scapulae   . 

.     63 

Eustachian  tube  . 

.  137 

-  ilii  .         .         . 

.     83 

Extremities,  anterior, 

see  Fore 

Drum  of  the  ear,  see 

Tym- 

limb. 

panum. 

—  posterior,  see  Hin 

1  limb. 

Ducts,  bile   . 

.  225 

Eye 

.  146 

—  of  glands 

.     19 

—  muscles  of 

.  144 

—  hepatic   . 

.  225 

Eyeball 

.  146 

JiUt) 

INDEX. 

PAGE 

PAGE 

Eyelids 

.    120 

Fimbriated  extremity   . 

.  249 

Eyelid,  third 

.  143 

Fissure          .         . '      . 

.     10 

Eyelashes 

.  121 

Fissures  of  spinal  cord  . 

.  181 

Excrescence,  cauliflower 

.  250 

—  cerebrum 

.  155 

External  ear 

122 

—  palpebral 

.  121 

Extremity,  dissection  of  fore  201 

—  of  Sylvius 

.  161 

—     —  of  hind    . 

.  257 

—  of  liver,    transverse 
Flat  bones    . 

.  225 
.       9 

Face      .... 

.     24 

Fixed  joints 

.     99 

—  bones  of  . 

.     33 

Fleur  epanouie 

.  250 

Facial  nerve 

.  119 

Flexure,  sigmoid,   of  double 

Falciform  ligament  of  bladder  241 

colon     . 

234 

—     —  of  liver    . 

.     22 

Foal,  peculiarities  of    . 

255 

Fallopian  tube 

.  249 

Foetal  appendages 

253 

False  nostril 

.  116 

—  circulation 

253 

—  ribs 

.     58 

Follicular  glands  . 

18 

—  tongues  . 

.  254 

Follicles  of  Lieberklihn 

232 

—  vertebrse 

.     44 

Fontaua,  canal  or 

148 

Falx  cerebri . 

.  153 

Foot     .... 

273 

Fang  of  tooth 

.  128 

—  bones  of . 

281 

Faschia  or  fascia  . 

.     11 

—  nerves  of 

287 

—  of  arm     . 

.  210 

—  vessels  of 

280 

—  abdouiinalis   superf. 

.  216 

—  tendons  of 

287 

—  cremasteric    •  . 

.  245 

Foramen    auditorium    exter- 

— intercolumnar 

.  245 

num 

32 

152 

—  lata 

.  258 

—     —  internum 

32 

,151 

—  lumbar    . 

.  183 

—  communicating  anterior  . 

157 

—  psoas 

.  256 

—     —  posterior  . 

158 

—  of  quarter 

.  257 

—  condyloideum 

25*, 

151 

Fasciculi  of  muscle 

.     12 

—  dextrum. 

188 

Fat  in  orbit . 

.  143 

—  incisorum 

34 

Fatty  mane  . 

.  166 

—  infra-orbitale  . 

35 

Fauces,  isthmus  of 

.  137 

—  lacerum  basis  cranii 

151 

—  pillars  of 

.  137 

—     —  orbitale    . 

30,' 

152 

Feelers 

.  120 

—  lachrymal 

37 

Female  generative  organs 

.  273 

—  magnum  occiputum 

151 

Femoral  space 

.  260 

—     —  vertebral 

49 

Fenestra  ovalis     . 

.  164 

—  maxillary,  anterior 

41 

—  rotunda  . 

.  164 

—     —  posterior  . 

41 

Fenestrated     membrane 

of 

—  medullary 

9 

Henle    . 

.     21 

—  menti 

41 

Fibres  of  Corti     . 

.  164 

—  of  Monro 

157 

—  nerve 

.     14 

—  obturator 

84 

—  muscle     . 

.     12 

—  optic 

152 

Fibrillar 

.     12 

—  orbitale  internum    . 

152 

Fibro-cartilage 

.      7 

—  ovale 

196, 

254 

Fibrous  coronary  band 

.  280 

—  palato-maxillary 

38 

Fibrous  tissue 

.       7 

—  pathetic  . 

152 

Fibular   arch 

.     92 

—  rotundum 

30, 

152 

Filiform  papillse   . 

.  133 

—  siuistrum 

189 

Filum  terminals  . 

.  180 

—  Soemering 

148 

INDEX. 


297 


Foramen,  spheno-palatine 

PAGE 

.    37 

Ganglion,  Inferior 

—  styloid    .         .         .32,  152 

—  lenticular 

—  subsacral 

.     56 

—  middle     . 

—  subsphenoidal 

.     30 

—  Meckel's 

—  snpersacral 

.     56 

—  ophthalmic 

—  sxipra-orbital    . 

.     28 

—  otic 

—  of  Winslow      . 

.  223 

—  semilunar 

Foramina      . 

.     10 

—  post-meseuteric 

—  articular 

.       9 

Ganglionic  nervous  system 

—  of  cranium 

.  151 

Gaps,  intervertebral 

—  intervertebral 

.     43 

Gastric  glands 

—  Thebesii  . 

.  197 

Gastro-hepatic  omentum 

Fore  limb,  articulations  of 

.  106 

—  jihrenic  omentum    . 

—  bones  of 

.     61 

—  splenic  omentum 

—  dissection  of    . 

.  201 

—  colic  omentum 

Foreskin 

.  244 

Generative  organs,  female 

Fornix 

.  381 

—     —  male 

Fossa    .... 

.     10 

Geniculata,  corpora 

—  antea  spinatus 

.     63 

Genu  of  corpus  callosum 

—  ethmoid 

.  150 

Ginglymoid  joint 

—  intercondyloid  (femur) 

.     88 

Glands 

—  navicularis,  male      . 

.  243 

—  Brunner's 

—     —  female      . 

.  251 

—  buccal      . 

—  olfactory 

.     30 

—  ceruminous      . 

—  optic 

.     29 

—  Cowper's 

—  ovalis 

.  197 

—  ductless  . 

—  postea  spinatus 

.     63 

—  gastric     . 

—  renal 

.  239 

—  labial       . 

—  temporal 

.  125 

—  lachrymal 

—  trochanteric     . 

.     86 

—  of  large  intestine      . 

Frsenum  linguse    . 

.  133 

—  lymphatic 

Frgena  (synovial) 

.     15 

—     —  inguinal 

Freely  moveable  joints 

.  100 

—     —  popliteal 

Fringes,  synovial 

.     15 

—     —  mesenteric 

Frog-,  liorny 

.  276 

—  lymphatic  axillary  . 

—  sensitive 

.  280 

—     —  bronchial 

—  fibrous  or  fatty 

.  280 

—     —  prescapular 

—  stay 

.  276 

—     —  parotid     . 

Frontal  sinus 

.  142 

—  mammary 

Fundus  of  bladder 

.  241 

—  Meibomian 

Fungiform  papillae 

.  133 

—  mucous,  of  stomach . 

Furrows 

.     10 

—  molar,  see  Buccal. 

—  of  heart  . 

.  196 

— •  ofPacchioni 

Galactophorous  sinuses 

.  252 

—  palatine  . 

G.ill  duct,  see  Bile  duct. 

—  pancreas 

Ganglia 

.     13 

—  parotid    . 

—  of  heart  . 

.  200 

—  peptic      . 

Gangliated  cord    . 

.  195 

—  Pej'er's   . 

Ganglion,  Arnold's,  see  Otic. 

—  prostate 

—  cervical,  superior 

.  178 

—  salivary  . 

—  Gasserian 

.  126 

—  sebaceous 

%y« 

INDEX. 

PAGE 

) 

PAGE 

Glands,  of  skin     . 

.     17 

Heart,  cavities  of 

;  197 

—  of  small  intestine     . 

.  232 

—  chordae  tendincEe      . 

.  198 

—  solitary    . 

.  232 

—  columnas  carnea3 

.  198 

—  sublingual  salivary  . 

.  133 

—  corpora  arantii 

.  199 

—  submaxillary  salivary 

.  167 

—  endocardium   . 

.  196 

—  sudoriparous    . 

.     17 

—  fibrous  rings  of 

.  196 

—  thymus    . 

.  200 

—  foetal       . 

.  254 

Glaus  penis 

.  241 

—  foramina  Thebesii    . 

.  197 

Glenoid  cavity 

.     10 

—  fossa  ovalis      . 

.  197 

Glisson's  capsule  . 

.  226 

—  furrows  . 

.  196 

Globe  of  the  eye    . 

.  146 

—  lining  membrane     . 

.  196 

—  epididymis 

.  247 

—  muscular  fibres  of    . 

.  197 

Glosso-pharyngeal  nerve 

.  139 

—  musculi  papillares    . 

.  198 

Glottal  opening     . 

.  175 

—     —  pectinati . 

.  197 

Glottidis,  rima 

175 

—  nerve  supply   . 

.  200 

Gomphosis    . 

99 

—  orifice,  auriculo-ventricu 

Graafian  vesicles  . 

248 

lar,  right 

.  197 

Grey  nerve-fibres 

13 

—    —    —  left  . 

.  199 

Gristle,  see  Cartilage. 

—     —  pulmonary 

.  198 

Groove 

10 

—     —  aortic 

.  199 

—  primitive  dental 

130 

—  sinus  Valsalvae 

199 

Gubernaculum  testis 

246 

—  systemic. 

.  196 

Gullet,  see  CEsophagus. 

—  tuberculum  Loweri . 

.  197 

Gums    .... 

128 

—  valves,  auriculo-ventricu 

Gustatory  nerves 

136 

lar,  right 

197 

Guttural  pouches 

137 

—     —     —  left  . 

199 

Gyri     .... 

155 

—     —  Eustachian 

197 

Gyrus  fornicatus 

155 

—     —  mitral  or  bicuspid 

199 

—     —  pulmonary 

196 

Ha3mal  arch          .         .      42 

,150 

—     —  semilunar  aortic 

199 

—  spine       .         .         .         . 

43 

—     —     —  pulmonary 

198 

Hsemorrhoidal,  see  Rectal. 

—     —  systemic  . 

196 

Hair 

17 

—     —  Thebesii  . 

197 

—  follicles  .         .         .         . 

17 

—  ventricle,  right 

198 

—  root         .         .         .         . 

17 

—     —  left 

199 

—  stem        .         .         .         . 

17 

Heart's  lymph 

23 

—  bulb        .         .         .         . 

17 

Hemispheres  of  brain  . 

155 

Hamular  process  of  ulna 

71 

—  cord         .          .         .         . 

181 

Harmonia     .         .         .         . 

99 

Hepatic  cells 

226 

Haversian  canals  . 

8 

—  duct         .         .         .         . 

225 

—  systems  .         .         .         . 

8 

Hiatus          .         .         .         . 

10 

Haw,  see  Cartilago  nictitans. 

—  aorticus  .         .         .         . 

188 

Head,  dissection  of 

115 

—  sphenoideal  or  orbital 

152 

—  bones  of . 

24 

Hilum  of  kidney  . 

239 

Heads 

10 

—  spleen     .         .         .         . 

236 

Heart 

192 

Hind  limbs  .          .         .         . 

257 

—  annulus  ovalis 

197 

—  joints  of . 

111 

—  arteries  of        .         .         . 

194 

Hip-joint      .         .         .         . 

10 

—  auricles  of  riglit 

197 

Hippocampus 

157 

—     —  left .         .         .         . 

199 

Hippotomy  .          .         .          . 

1 

—     —  appendices 

199 

Histology     .         .         .         . 

1 

IND'EX. 


299 


Hock-bones . 

PAGE 

.     92 

PAGE 

Intestines,      large,     sigmoid 

—  joint 

.  113 

flexure 

.  234 

Hoof    . 

.  273 

—     —  mucous  membrane  of  230 

—  hind 

.  278 

—     —  muscular  coat  of      .  232 

—  commissures    . 

.  274 

—     —  rectum     . 

.  235 

—  coronary  frog-band 

.  275 

—    —  serous  coat  of 

.  231 

—  frog  of    . 

.  277 

—  small,  duodenum 

.  233 

^-  frog- stay  of    . 

.  277 

—     —  glands  of 

.  232 

—  heels  of  . 

.  274 

—     —  ileum 

.  233 

—  horn  of   . 

.  274 

—     —  jejunum  . 

.  233 

—  laminae  of 

.  275 

—     —  mucous  membrane  of  232 

—  quarters  of 

.  274 

—     —  muscular  coat  of       .  232 

—  sole  of     . 

.  276 

—     —  serous  coat  of 

.  231 

— -  toe  of      . 

.  274 

Intralobular  veins 

.  226 

—  wall  of    . 

.  274 

Involuntary  muscle 

.     11 

Horn    . 

.  271 

Iris       . 

.  148 

—  secreting  layer 

.     80 

Irregular  bones    . 

.       9 

Horsehair     . 

.     18 

Ischial  arch  . 

.    85 

Humour,  aqueous 

.  149 

Ischium 

.     84 

—  third 

.  149 

Isthmus  of  the  fauces 

.  158 

—  vitreous  . 

.  149 

Iter  a  tertio  ad  quartum  ven- 

Hymen 

.  251 

triculum 

.  158 

Hypochondriac  regions 

.  231 

Iter  e  cerebello  ad  testis        .  158 

Hj-pogastric  plexus 

.  227 

—  region     . 

.  231 

Jacobi,  tunica 

.  148 

Hypoglossal  nerve 

.  136 

Jacobson's  canal  . 

.  141 

Jaw,  lower  . 

.     24 

Heo-csecal  valve   . 

.  233 

—  upper 

.     24 

Heum  . 

.  233 

Jejunum 

.  233 

Iliac  artery,  external     . 

.  238 

Joints,  amphiarthrotic 

.  100 

—     —  internal    . 

.  238 

—  arthrodial 

.  100 

Ilium    . 

.     82 

—  atlaxoid 

.  102 

Imprint 

.     10 

—  atloido-occipital 

.  102 

Incisions    (primary,  th 

rough 

—  axonoides 

.  101 

skin)      . 

.       4 

—  carpal      . 

.  107 

Incisors 

.  129 

—  carpo-metacarpal 

.  107 

Incisive  opening  . 

.     34 

—  coflin 

.  109 

Incus  .         .         .         . 

.  164 

—  costal 

.  105 

Inferior  maxillary  sinus 

.  142 

—  diarthrodial     . 

.  100 

Infundibulum 

.  161 

—  elbow 

.  106 

Inf  undibuli . 

.  129 

—  fetlock    . 

.  108 

Inguinal  canal 

.  219 

—  fixed        . 

.     99 

Injection  of  vessels 

.       2 

—  of  fore  extremity 

.  106 

Inosculation 

.     21 

—  ginglymus 

.  100 

Instruments 

.       2 

—  harmonia 

.     99 

Interlobular  veins 

.  226 

—  of  hind  extremity  . 

.  Ill 

Intestines     . 

.  231 

—  hip 

.  Ill 

—  large 

.  234 

—  hock 

.  113 

—     —  cfficum      . 

.  234 

—  hyoid 

.  134 

—     —  colon,  double    . 

.  234 

—  knee 

.  107 

—     —     —  single 

.  235 

—  moveable 

.    99 

300 


INDEX. 


PAGE 

Joints,  partially  inoveaLIe  .  100 

—  pastern   .         .         .  .109 

—  pedal       .         .         .  .109 

—  radio -carpal     .         .  .  107 

—  —  ulnar        .         ,  .106 

—  shoulder          .         .  .  106 

—  schindylesis     . 

—  stifle        .         .         .  .111 

—  sutural    .         .         .  .99 

—  synarthrodial  .         .  .99 

—  tarsal       ....  113 

—  tarso-metatarsal      .  .113 

—  vertebral         .         .  .  103 


Kidney 

.  239 

—  adipose  tunic  of 

.  239 

—  calyces    . 

.  240 

—  capsule   . 

.  239 

—  corpuscles  of  Malpighi 

.  240 

—  cortical  substance    . 

.  240 

—  hilum 

.  239 

—  left 

.  239 

—  medullar)?  substance 

.  240 

—  pelvis  of . 

.  240 

—  pyramids  of  Malpighi 

.  240 

—  right 

.  239 

Knee    .... 

.     71 

—  joint 

.  107 

Labia,  see  Lips. 

—  majora     . 

—  minora  . 
Labyrinth  . 
Lachrymal  canals 

—  foramen  . 

—  gland 

—  puncta     . 

—  sac 

—  tubercle  . 
Lacuna? 

—  of  urethra 
Lacteals 

Lambdoidal  suture 
Lamina  ci'ibrosa 

—  spiralis  . 
Laminae  of  bone 

—  vertebra 

—  horny 

■ —  sensitive 
Larynx 


.  251 
.  251 
.  163 
.  143 
.  37 
.  143 
.  143 
.  143 
.  36 
.  8 
.  241 
23,  227 
.  102 
.  146 
.  164 
.  8 
.  42 
.  275 
.  279 
.  173 


PACK 

Laryns,  cartilages  of 

.  174 

—      —  arytenoid 

.  175 

—     —  cricoid 

.  174 

—     —  epiglottis 

.  174 

—     —  thyroid     . 

.  173 

—  ligaments 

.  175 

—  mucous          membrane  of  176 

—  muscles  of 

.  176 

—  nerves  of 

.  177 

—  ventricles  of 

.  176 

—  vocal  cords  of 

.  175 

Lateral  cartilage  of  foot        .  284 

Leg,  see  Limb. 

Lens,  crystalline  . 

.  149 

—  capsule  of 

.  149 

Lenticular  ganglion 

.  145 

Lieberkiihn's  follicles 

.  232 

Ligaments    . 

.  119 

—  annular   . 

.     11 

—  of  bladder 

.  222 

—  calcaneo-cuboid 

.  114 

—  capsular  . 

.     11 

—  cardiac    . 

.  219 

—  of  bladder 

.  241 

—  ciliary      . 

.  148 

—  coraco-scapular 

.     62 

—  cotyloid  . 

.  Ill 

—  crico-trachealis 

.  176 

—     —  thyroid     . 

.  173 

—  crucial,  of  stifle 

.  112 

—  denticulatum  . 

.  ISO 

—  extensor  um 

.  212 

—  interspinous     . 

.  104 

—  of  liver    . 

.  233 

—  nuchse 

.  104 

—  obturator 

.  Ill 

—  odontoid 

.  103 

—  of  patella 

.  112 

—  of  the  pelvis    . 

.  109 

—  Poupart's 

.  219 

—  pubis  femoral 

.  Ill 

—  sacral 

.  104 

—  stellate    . 

.  105 

—     —  of  navicular 

.  286 

—     —  of  rib 

.  105 

—  subcarpal 

.  210 

—  superior  sesamoidea 

I         .  208 

—  supra-spiuous 

.  104 

—  suspensory,  superior 

.  210 

—       —  penis 

.    216,245 

—  tarsi 

.  120 

INDEX. 

301 

Ligaments,  triangular  penis 

PAGE 
.        8i 

PAGE 

Malpighian     corpuscles     of 

Limb,  see  Extremities. 

spleen   . 

.  236 

—  bones  of  fore    . 

.     61 

—  pyramids 

.  240 

—     —  hind 

.     82 

Mammary  glands 

.  252 

—  articulations  of  fore 

.  106 

—  ducts  of 

.  252 

—     —  hind 

.  Ill 

—  sinuses  of 

.  252 

Linea  alba     . 

.  228 

Marrow 

.       8 

Lips      .... 

.  119 

Mastoid  cells 

32,  164 

Liquor  Morgagni  . 

.  150 

—  lobule 

.  161 

Liver,  cells  of 

.  226 

Maxillary  sinuses 

.  142 

—  circulation  through 

.  226 

Meatus,  auditory,  external    .  123 

—  excretory  apparatus  of 

.  224 

—     —  internal 

.  243 

—  Glisson's  capsule  of 

.  226 

—  of  nasal  chambers 

.  141 

—  ligaments  of   . 

.  223 

Mediastina   . 

.  189 

—  lobes  of  . 

.  225 

Mediastinum  testis 

.  286 

—  lobulus  caudatus 

.  225 

Medulla  spinalis,  see  Spinal 

—     —  scissatus  . 

.  225 

cord. 

—     —  vessels  of 

.  226 

—  oblongata 

.  159 

Lobes  of  cerebrum 

.  161 

—  ossium,  see  Marrow 

—  cerebellum 

.  159 

Medullary  canal    . 

.      8 

—  liver 

.  225 

—  foramen  . 

.       9 

—  lungs 

.  191 

—  matter  of  brain 

.  156 

Lobule,  mastoid    . 

.  161 

— •     —  kidney 

.  240 

Lobules  of  liver    . 

.  225 

—     sheath   . 

.     14 

—  testis 

.  246 

Meibomian  glands 

.  120 

Lobulus  caudatus 

.  225 

Membrana  decidua 

.  250 

—  scissatus 

.  225 

—  fusca 

.  147 

Locus  perforatus  anticus 

.  161 

—  nictitans 

.  142 

—     —  posticus    . 

.  161 

—  pupillaris 

.  149 

Longitudinal  sinus 

.  153 

—  tympani 

.  164 

Long  round  bones 

.       8 

Membrane  of  Demeurs 

.  149 

Linear  bone 

.     72 

—  of  Descemet     . 

.  149 

Lungs,  air-cells  of 

.  191 

—  hyaloid    . 

.  149 

—  lobes  of  . 

.  191 

—  simple 

.     14 

—  roots  of  . 

.  191 

—  compound 

.    15 

—  vessels,  pulmonary  . 

.  196 

—  mucous 

.     16 

—     —  bronchial 

.  192 

—  serous 

.     15 

Lutea,  macula 

.  148 

—  Schueiderian  . 

.  286 

Lymph  hearts 

.     23 

—  synovial 

.    15 

—  spaces 

.     23 

—  tentorial 

,  153 

Lymphatics 

.     22 

—  winking 

.  143 

—  glands,  see  Glands. 

Membranes  of  brain 

.  153 

—  afferent    . 

.     23 

—  fcetus 

.  253 

—  efferent  . 

.     23 

—  spinal  cord 

.  180 

Membranous  labyrinth 

.  163 

Macula  lutea 

.  148 

—  semicircular  canals 

.  163 

Male  generative  organs 

.  243 

—  urethra    . 

.  242 

Malleolus 

.     91 

Meninges,  see  Membrar 

es. 

Malleus 

.  165 

Mesentery     . 

.  226 

Malpighian  corpuscles  of  kid 

- 

Meso-csecum 

.  222 

ney 

.  240 

—  colon 

.  222 

3oa 


INDEX. 


PAGE 

PAGE 

Meso-csecum,  rectum 

222 

Muscles,  buccinator      . 

118 

Milk     . 

'.  252 

— 

caninus  .... 

118 

—  teeth 

.  129 

— 

caput  magnum 

203 

Mitral  valve 

.  199 

— 

—  medium    . 

203 

Moderator  bands 

.  198 

— 

—  parvum    , 

204 

Modiolus 

.  163 

— 

cervical  trapezius     . 

183 

Molar  teeth  . 

.  130 

— 

complexus  major 

171 

Mou  orchid    . 

.  246 

— 

—  minor 

171 

Monro's  foramen  . 

.  157 

— 

compressor  coccygis 

272 

Morgagni,  liquor  . 

.  150 

— 

constrictors  of  pharynx    . 

138 

Motor  nerve-roots 

.  181 

— 

coraco-humeralis 

204 

Motores  oculorum 

.  145 

— 

—  radialis     . 

202 

Motorial  plates 

.     14 

— 

cornealis  transversus 

140 

Mouth  c         .         .         . 

.  127 

— 

costarum  superticialis 

104 

Moveable  joints     . 

.  100 

— 

—  transversalis     . 

104 

Mucous  membrane 

.     16 

— 

—  levatores 

186 

—  of  intestines     . 

.  232 

— 

crico-arytennideus  posticus  176 

—  lachrymal  apparatus 

.  121 

— 

—  lateralis 

176 

—  larynx 

.  175 

— 

—  pharyngeus 

138 

—  mouth     . 

.  133 

— 

—  thyroideus 

176 

—  nose 

.  141 

— 

curvator  coccygis    . 

272 

—  oesophagus 

.  172 

— 

depressor  ani  . 

235 

—  palate 

.  138 

— 

—    coccygis 

272 

—  pharynx  . 

.  138 

— 

—  labii  superioris 

119 

—  stomach  . 

.  229 



—  oculi 

144 

—  tongue     . 

.  133 

— 

detrusor  urinse         .    13C 

,242 

—  trachea    . 

.  178 

— 

diaphragm 

188 

—  tympanum 

.  165 

— 

digastricus 

135 

—  ureters     . 

.  240 

— 

dilator  naris  anterior 

140 

—  urinary  bladder 

.  241 

— 

—     —  inferior     . 

119 

—  uterus 

.  250 

— 

—     —  superior    . 

116 

—  vagina     . 

.  251 

— 

of  external  ear,  extrinsic 

123 

—  vvilva 

.  251 

— 

—  intrinsic  . 

122 

Muscles 

.     11 

— 

of  internal  ear 

165 

—  voluntary 

.     12 

— 

erector  coccygis,  see  Le- 

—  involuntary 

.     12 

vator. 

—  varieties  of 

.     12 

— - 

extensor  metacarpi  maguus 

—  abdominal 

.  219 

211 

—  abductor  oculi 

.  144 

_ 

—     —  obliquus 

211 

—     —  of  ear 

.  144 

__ 

—  pedis 

212 

—  accelerator  urinse     . 

.  244 

— 

—     —  (hind) 

260 

—  adductor  oculi 

.  144 

— 

—  suffraginis 

212 

—     —  auris 

.  123 

— 

flexor  brachii  . 

202 

—  anconeus 

.  205 

— 

—  metacarpi  externus  . 

213 

—  of  anus    . 

.  335 

— 

—     —  medius 

209 

—  antea  splnatus 

.  202 

— 

—     —  internus    . 

209 

—  attolentes  aurum 

.  126 

— 

—  metatarsi 

269 

—  attrahentes  aurum 

.  120 

— 

—  pedis  accessorius 

269 

—  auricular 

.  126 

— 

—     —  perf(jrans     210, 

269 

—  biceps  adductor  fern 

oris   .  261 

— 

—     —     —  hind  . 

269 

—     —  rotator  tibialis 

.  259 

— 

—     —  perforatus 

210 

INDEX. 


303 


PAGE 

Muscles  gastrocnemius  exter- 

nus        .         .         .         .  267 

—  —  iuternus  .         .         .  268 

—  gemini     ....  267 

—  genio-liyoideus         .         .  134 

—  —  liyoglossus        .         .  134 

—  gluteus  externus      .         .257 
■^—     —  interims   .         .         .  258 

—  —  maximus  .         .  258 

—  —  medius,  see  Maximus  258 

—  gracilis    ....  260 

—  liumeralis  externus  .  205 

—  h,yo-epiglottideus     .         .174 

—  hyoglossus  brevis     .         .  134 

—  —  lougus      .         .         .  135 

—  —  parvus      .         .         .  185 

—  hyo-pharyngeus        .         .  138 

—  hyo-thyro-pbaryngeus      .  138 

—  hyoideus  magnus     .         .135 

—  —  parvus      .         .         .  135 

—  —  trans  versus        .         .134 

—  iliacus      .         .         .  .261 

—  ilio-femoralis  .         .  .  262 

—  inferior  oblique,  of  eye  .  144 

—  intercostal!  s  externus  .  186 

—  —  internus   .         .   186,  218 

—  intertransversalis  colli      .  179 

—  —  dorsi         .         .         .186 

—  iscbio-femoralis        .         .  267 

—  —  tibialis      .         .         .259 

—  —  trocbanterius    .         .  267 

—  of  larynx  .  .  .  176 

—  lateralis  sterni  .  .  218 

—  latissimus  dorsi  .  .  183 

—  levator  ani       .  .  .  235 

—  —  coccygis  .         .         .  272 

—  —  costse        .         .         .  186 

—  —  bumeri     .         .    169,  201 

—  —  labii  superioris  alseque 
nasi       ....   115 

—  —  palpebrae    superioris 
externus         .         .         .  120 

—  —     —     —  internus     .  143 

—  —  oculi         .         .         .  144 

—  longissimus  dorsi  .  .  184 

—  longus  colli      .  .  .  178 

—  lambrici  .         .  .  .109 

—  masseter  externus  .  .  116 

—  —  internus   .         .         .  123 

—  moutb,  wbicb  close  .  125 

—  mylo-byoideus  .         .  123 


Muscles,  nasalis  longus  labii 

superioris       .         .         .  116 

—  obliquus  abdominis  exter- 

nus        ....  220 

—  —     —  internus    .         .  220 

—  —  capitis  auticus  .         .  170 

—  —     —  inferior      .         .  170 

—  —     —  superior     .         .  170 

—  obturator  externus  .  267 

—  —  internus   .         .         .  267 

—  orbicularis  oris         .         .  120 

—  —  palpebrarum     .         .  120 

—  palato-pharyngeus  .         .  137 

—  panniculus      .    115,  166,  216 

—  parotides  auricularis        .  166 

—  pectineus 

—  pectoralis  anticus     . 

—  —  magnus    . 

—  —  transversus 

—  peroneus 

—  of  pharynx 

—  plantaris 

—  popliteus 

—  postea  spinatus 

—  psoas  magnus  . 

—  —  parvus 

—  peterygoideus . 

—  pyriformis 

—  radialis  accessorius  . 

—  rectus  abdominis 


261 
217 
217 

217 
269 
138 
268 
268 
202 
255 
256 
124 
267 
210 
220 


—  —  capitis  anticus  major  179 

—  —     —     —  minor         .  179 

—  —     —  posticus  major  .  171 

—  —    —     —  minor          .  171 

—  —  feraoris     .         .         .  262 

—  retractor  ani    .         .         .  235 

—  —  anguli  oris        .         .  115 

—  —  costse        .         .         .  220 
— -     —  labii,  inferioris          .  116 

—  —     —  superioris           .  116 

—  —  lingualis  .         .         .  134 

—  —  penis         .         .         .  244 

—  retrahentes  aurum  ,         .  166 

—  rbomboideus   .         .         .  183 

—  sartorius          .         .         .  260 

—  scalenus           .         .         .  178 

—  scapulo  -  bumeralis  exter- 

nus       ....  203 

—  —     —  posticus    .         .  205 

—  • —  -ulnaris    .         .         .  205 

—  scuto-^uricularis  externus  122 


45Ui 

INDEX. 

PAGE 

PAGE 

Muscles,  scuto-auriculai 

'is  in- 

Myeloplaxes 

.       8 

ternus  . 

.  122 

Myolemma,  see  Sarcoid 

mma. 

—  semimembranosus    . 

.  259 

Muzzle. 

.     24 

—  semispiualis  dorsi,  &. 

c.      .  186 

—  semitendinosus 

.  259 

Naboth's  glands    . 

.  250 

—  serratus  magnus 

.  218 

Nares,  anterior     . 

.  139 

—     —  parvus  anterior 

.  184 

—  posterior 

.  138 

—     —     —  posterior  . 

.  183 

Nasal  cartilages    . 

.  139 

—  sphincter  ani  . 

.  235 

—  chambers 

.  139 

—     —  vesicse 

.  242 

—  fossae  or  cavities 

.  139 

—  spinalis  dorsi  . 

.  185 

—  mucous  membrane 

.  145 

' —     —  colli,  &c.  . 

.  179 

—  nerve 

.  145 

—  splenius  . 

.  170 

—  openings 

.  139 

—  sterno-maxillaris     . 

.  167 

—  peak 

.     33 

—     —  -thyro-hyoideus 

.  167 

Nates   . 

.  158 

—  stapedius 

.  165 

Navicular  fossa     . 

.  243 

—  stylo-maxillaris 

.  168 

—     —  female 

.  257 

—     —  -pliaryngeus     . 

.  139 

Neck,  dissection  of 

.  166 

—     —  -hyoideus 

.  136 

—  of  tooth . 

.  128 

—  subscapularis  . 

.  204 

Nerve  . 

.     13 

—  subscapulo-hyoideus 

217,  200 

—  cells 

.     14 

—  superior  oblique,  of  e 

ye   .  144 

—  fibres       . 

.     14 

—     —  of  tail      . 

.  272 

—  tissues     . 

.     13 

—  temporalis 

.  124 

Nerve,  abduceus  . 

.  145 

—  tensor  palati    . 

.  137 

—  auditory. 

.  164 

—     —  tympani  . 

.  165 

—  auricular 

.  182 

—     —    vagina3  femoris 

.  258 

—  axillary  plexus 

.  207 

—  teres  externus  v.  mir 

lor   .  203 

—  brachial,  see  Axillai 

y- 

internus  v.  major 

.  204 

—  bronchial  plexus 

.  192 

—  thyro-arytenoideus 

mti- 

—  buccal  (of  fifth)       . 

.  119 

cas 

.  176 

—  cardiac    . 

.  195 

—     —     —  posticus    . 

.  176 

—  cervical    . 

.  182 

—     —  -hyoideus. 

.  176 

—  chorda  tympani 

.  124 

— pharyngeus     . 

.  138 

—  coccygeal 

.  272 

—  of  tongue 

.  134 

—  crural 

.  266 

• —  trachelo-mastoideus 

.  170 

—  dental,  superior 

.  127 

—  trachealis  transversu 

5      .  177 

—  diaphragmatic,  see  F 

hrenic. 

—  transversalis  abdomir 

lis    .  221 

—  eighth  cranial. 

.  164 

—     —  costarum 

.  184 

—  eleventh  cranial 

.  163 

—  trapezius 

.  183 

—  facial       .         .     lis 

,  126, 148 

—  triceps  abductor  feme 

)ris  .  258 

—  fifth  cranial     . 

.  127 

—     —  extensor  brachii 

.  203 

—  first  cranial      . 

.  148 

—     —     —  cruralis     . 

.  262 

—  fourth  cranial . 

.  145 

—  ulnaris  accessorius  . 

.  210 

—  glosso-pharyugeal    . 

.  139 

—  vastus  externus 

.  262 

—  gluteal    . 

.  266 

—     —  internus  . 

.  262 

—  gustatory 

.  124 

—  Wilson's 

.  242 

—  hypoglossal 

.  136 

—  zygomaticus    . 

.  115 

—  intercostal 

.  404 

Musculi  pectinati 

.  197 

—  laryngeal,  superior  . 

.  177 

—  papillares 

.  198 

—     —  inferior     . 

.  177 

Musculus  ciliaris  v.  Ugar 

aent  148 

—  lingual     . 

.  136 

IXDEX. 


305 


PAGE 

Nerve,  lumbar      .         .         .265 

—  maxillary,  superior  .         .127 

—  —  inferior     .         .         .  124 

—  metacarpals     .         .         .  287 

—  metatarsals      .         .         .  272 

—  motores  oculorum    .         .  145 

—  Basal,  lateral    .         .         .  145 

—  jimth       .         .         .         .139 
--  obturator  .         .         .  266 

—  olfactory  .         .         .  141 

—  Oi^bthalmic,  of  fifth  .         .  145 

—  optic        ....  148 

—  palato-maxillary      .         .  127 

—  pathetic  ....  145 

—  phrenic  ....  178 

—  plantar    ....  287 

—  pueumogastric  .         .  177 

—  popliteal ....  271 

—  portio  dura      .         .         .  164 

—  portio  mollis    .         .         .  164 

—  radial      ....  207 

—  recurrent         .         .         .  177 

—  sacral       ....  268 

—  scapular  ....  207 

—  sciatic     ....  266 

—  seventh  ....  164 

—  sixth        ....  145 

—  spinal  accessory       .         .  182 

—  spiral       ....  207 

—  splanchnic        .         .         .  195 

—  subscapular      .         .         .  207 

—  suboccipital     .         .         .  182 

—  supra-orbital    .         .         .  145 

—  sympathetic    .         .         .  195 

—  third  cranial    .         .         .  145 

—  tibial,  anterior         .         .271 

—  —  posterior  .         .         .  272 

—  twelfth   .         .         .         .136 

—  ulnar       ....  207 

—  vertebral  .         .         .195 

—  vestibular        .         .         .164 

—  vidian  ....  127 
Nervosa,  tunica  .  .  .  148 
Nervus  vagus,  see  Pneumogastric. 
Neural  arch  .  .  .  150 
Neurilemma  .  .  .14 
Nipples,  see  Teat. 
Non-articulatery  eminences  .  9 
Non-ciliated  epithelium  .  16 
Nostril,  fiilse  .  .  .  124 
Notch  .         .         .         .         .10 


PAGE 

Xotch,  intervertebral,  jee  Gap  143 

—  isciiiatic  ....  110 
Nuckse,  ligamentum      .         .  104 

Oblique  muscles  of  abdomen  220 

—  —  eye  .         .         .         .  144 

—  flexor  of  metacarpus  .  211 
Oblongata,  medulla  .  .  159 
Obturator  foramen  .  .  84 
Occiput  .  .  .  .24 
Occipital  sinuses  .  .  .  154 
Odontoid  ligaments       .         .  103 

—  process  .  .  .  .49 
Odoriferous  glands  .  .  244 
(Esophagus  ....  172 
Olecranon  .  .  .  .71 
01f;ictory  bulb      .         .         .160 

—  ibssa        .         .         .         .30 

—  nerve       ....  160 

—  sinuses  .  .  .  ,150 
Olivary  bodies  .  .  .159 
Omenta,  gastric  .  .  .  223 
Openings,  pupillary  .  .  148 
Ophthalmic  ganglion  .  .  145 
Optic  decussation  .         .  160 

—  disc         .         .         .         .48 

—  fossa        .         .         .         ,29 

—  thalamus  .  .  .  157 
Ora  serrata  .  .  .  .147 
Orbiculare,  os  .  .  .  164 
Orbital  process  of  os  frontis  .     27 

.1 
Os,  see  Bone. 

—  planum   . 

—  uterinum  externum 

—  —  internum 
Ossicula  auditus  . 
Ossific  tentorium 
Ossification  . 

—  centres  of 
Osteology,  descriptive 
Otic  ganglion 
Otoconites    . 
Otolithes      . 
Ovale,  foramen 
Ovaries 

—  Graafian  vesicles  of 

—  ligaments  of    . 

—  tunica  albuginea  of 

—  structure 

—  artery  of 

20 


124 


248 
249 
164 

26 
7 
7 

24 
1^5 
163 
163 
254 
248 
248 
249 
248 
248 
238 


306 


INDEX. 


PAGE 

PAGE 

Ovum  . 

.  248 

Peptic  glands 

.  230 

Perforated  spaces  of  brain     .  161 

Paceliioni,  glands  of 

.  154 

Pericardium,  fibrous 

.  192 

Palate,  hard 

.  128 

—  serous 

.  193 

—  soft 

.  128 

Pericardial  sac 

.  193 

Palatine  arch 

.     38 

Perichondrium      . 

.  105 

—  canal 

.     36 

Perilymph    . 

.  163 

Palpebral  fissure  . 

.  121 

Perineum 

.  244 

Pampiniforme,  corpus 

.  246 

Peri-orbitale 

.  143 

Pancreas 

.  224 

Periosteum  . 

.       9 

Pancreatic  duct    . 

224 

Peristaltic  action  of  bowels  .  232 

Pauniculus  carnosus 

183,  216 

Peritoneum 

.  222 

Papillaj 

.     16 

Permanent  cartilaue 

.       7 

—  dental     . 

.  130 

—  teeth 

.  128 

—  hair-follicles    . 

.     17 

Pes  anserinus 

.  127 

—  skin 

.     17 

Petit's  canal 

.  147 

—  tongue    . 

.  133 

Peyer's  patches     . 

.  233 

—  of  bowels,  see  Villi 

.  232 

Pharynx 

.  138 

Papillary  layer  of  skin 

.     17 

Pia  mater  of  brain 

.  155 

—  stage   of   tooth   de^ 

i^elop- 

—     —  spinal  cord 

.  180 

ment     . 

.  130 

Pigmentary  layer  of  choroid  147 

Par     magnum,    see     l! 

^erve. 

Pillars  of  the  fauces 

.  137 

pneumogastric. 

—     —  tongue     . 

.  132 

Parietal  ridges      . 

.     26 

Pincers 

.        .  129 

Parotid  gland 

.  167 

Pineal  body  . 

.  158 

—  duct 

.  168 

Pituitary  body 

.  154 

Pars  trigemini 

.  126 

—  membrane 

.  140 

Partially  moveable  join 

ts       .  100 

Planum,  os    . 

.     28 

Patches,  Peyer's  . 

.  233 

Plates,  cribriform 

.     30 

Patella,  straight  ligame 

nts  of  112 

Pleura 

.  189 

Pathetic  nerve 

.  145 

Plexus 

.     14 

Pectinean  tubercle 

.     85 

—  axillary  . 

.  218 

Pectiniforme,  septum    . 

.  243 

—  choroides,  lateral  ventricle  155 

Pedicles 

.     42 

—     —  fourth  ventricle        .  155 

Pellucid  zone 

.  248 

—     —  hypogastric 

.  227 

Pelvis,  ligaments  of      . 

.  109 

—     —  solar 

.  227 

—  of  kidney 

.  240 

Pneumogastric  nerve 

.  177 

Pendulous    portion    of 

soft 

Polar  nerve- cells  . 

.     14 

palate    . 

.  138 

Pons  Varolii 

.  159 

Penis   .         .         .         . 

.  243 

Porta  of  liver 

.  225 

—  bulb  of   .         .         . 

.  244 

Portse  vena  . 

.  226 

—  corona  glandis  of'    . 

.  244' 

Portio  dura  . 

.  164 

—  corpus  cavernosum  ( 

)f      .  243 

—  mollis 

.  164 

—     —  spongiosum  of  . 

.  244 

Porus  opticus 

.  146 

—  crura  of 

.  243 

Pouches,  guttural 

.  137 

—  glansof 

.  244 

Poupart's  hgament 

.  219 

—  ligaments  of    . 

.  245 

Prteputium  clitoridis 

.  252 

—  meatus  urinarius  of 

.  243 

—  penis 

.  244 

—  muscles  of 

.  244 

Premolar  teeth     . 

.  132 

—  septum  pectiniforme 

of   .  243 

Prerenal  capsule  . 

.  236 

Penniform  muscle 

.     12 

Preservation  of  subject 

.       4 

INDEX. 

307 

PAGE 

PAGE 

Primitive  dental  groove 

.     130 

Ramus  anastomoticus   . 

.  168 

Process 

.        10 

—  of  inferior  maxilla  . 

.     41 

auditory,  external  . 

.     32 

Raphe  corporis  callosi  . 

.  156 

—  basilar,  of  occiput    . 

.     25 

—  scroti 

.  244 

—  coracoid,       of       inferior 

Receptaculum  chyli 

227 

maxilla  ... 

40 

Recti  muscles  of  eye     . 

.'  144 

—     —  scapula    . 

61 

Recto-vesical  folds 

.  241 

■^—  crista  galli 

29 

Rectum 

.  235 

—  haraular,  of  ulna 

77 

Rectus  abdominis 

.  220 

—  liyoid 

32 

Red  muscular  fibre 

.     12 

—  mastoid,  petrous  tempora 

32 

Renal  capsule 

.  239 

—     —  squamous  temporal 

31 

Reproductive      organs,      see 

—  oblique    . 

43 

Generative  organs. 

—  odontoid,  of  axis 

49 

Restiform  bodies  . 

.  160 

—  olecranon,  of  ulna    . 

71 

Rete  mirabile 

.    20 

—  palatine,  of  palatine  bone 

37 

—  mucosum 

.     17 

' —     —  of  anterior  maxilla  . 

34 

Reticulated  layer  of  skin 

.    17 

—     —  of  superior  maxilla    . 

36 

Retina 

.  148 

—  styloid  occiput 

25 

Retractor  ani 

.  235 

—     —  petrous  temporal 

32 

—  costal 

.  220 

—  spinous,  anterior  inferior. 

—  penis 

.  244 

of  ilium 

82 

Ribs 

.     56 

—     —  superior  posterior  of 

—  false        ... 

.     59 

ilium     .... 

83 

—  first 

.     59 

—     —  inferior    . 

43 

—  floating  . 

.     58 

—     —  superior  . 

42 

—  last 

.     60 

—  transverse 

43 

—  true 

-     58 

—  vermiform 

159 

Ridge 

.     10 

'• —  zygomatic        .         .         . 

31 

—  alveolar  . 

-     42 

Processes,  ciliary  . 

147 

—  mastoid  . 

.     25 

Prostate  gland 

243 

Rima  glottidis 

.  176 

Prostatic     portion     of     the 

Ring,  abdominal,  external 

.  219 

urethra 

242 

—     —  internal    . 

.  219 

Pterygoid  ligament 

'^38 

—  vertebral 

.     43 

Pubio-femoral  ligament  111, 

261 

Root  of  the  lung  . 

.  191 

Pulp  of  tooth 

129 

Rotatorial  joint    . 

.  101 

Puncta  lachrymalia         .  121 

143 

Round  ligament  of  bladder 

222 

—  vasculosa 

156 

—     —  liver 

.  223 

Pupil  of  the  eye    . 

148 

—     —  ovary 

.  224 

Pupillary  opening 

148 

—     —  uterus 

.  224 

Pylorus          .... 

229 

Ruyschiana  tunica 

.  147 

Pyramids  of  medulla  oblon- 

gata      .... 

160 

Saccular     stage      of     tootl 

I 

—  kidney     .... 

240 

development 

130 

Quadrigemina,  corpus  . 

158 

Saccules 
Sacs,  air 

163 
191 

Racemose  glands  . 

19 

Saggital  suture     . 

102 

Hadialis  accessorius 

210 

Salivary  glands     . 

118 

Radio-carpal  joint 

107 

.  Sarcolemma 

20 

—  -ulnar  arch 

69 

Sarcous  elements  . 

12 

—     —  articulation 

106 

Satellites      . 

12 

308 

INDEX. 

PAGE 

PAGE 

Scabrous  pits  of  occiput        .     26 

Solar  plexus 

227 

Scalae  of  cochlea  . 

.  163 

Sole,  horny  .... 

276 

Schiudyjesis 

.     99 

—  sensitive 

279 

Schneiderian  membran 

e        .  141 

Space,  femoral 

260 

Scissatus,  lobus    . 

.  225 

Spermatic  cord     . 

247 

Sclerotic 

.  146 

Sphenoideal  sinus 

142 

Scrotum 

.  245 

Spheroidal  epithelium  . 

16 

Scutiform  cartilages 

122 

Sphincter  ani 

235 

Sebaceous  glands  . 

!     18 

—  vesical     .... 

242 

Sella  turcica 

.     30 

Spigelii,  lobus 

225 

Semicircular  canals 

.  163 

Spinal  cord  .... 

180 

Semilunar  cartilages  of 

stifle  111 

—  column    .... 

42 

—  ganglion 

.  227 

Spines,  see  Processes,  spinous. 

Seminal  clucts 

.  241 

Splanchnic  nerves 

195 

—  vesicles    . 

.  241 

Spleen           .... 

235 

Seminiferous  tubes 

.  241 

—  arteries   .... 

236 

Sensitive  frog  of  foot 

.  280 

—  capsule    .... 

236 

—  sole                   — 

.  279 

—  curvatures 

236 

—  structures        — 

.  278 

—  hilum      .... 

236 

Sensory  roots  of  nerves 

.  181 

■ —  internal  structure    . 

236 

—  nerve  fibres 

.     13 

—  pulp        .... 

236 

Septum  lucidum   . 

.  156 

Splint  bones 

79 

—  nasi 

.  139 

—     —  hind 

98 

—  pectiniforme    . 

.  243 

Spongiosum,  corpus 

244 

—  scroti 

.  245 

Spongy  urethra    . 

243 

Serous  membrane 

.     15 

Squamous     epithelium,     see 

Sheaths  of  tendons 

.     15 

Tesselated. 

Sheath,  medullary 

.     14 

—  suture     .... 

99 

Short  bones 

.       9 

Stages  of  tooth  development 

130 

Shoulder-joint 

.  105 

Stapes           .... 

164 

Simple  glands 

.     18 

Stenson's  duct 

141 

Sinus 

.     10 

Steruo-costal  cartilages 

58 

—  of  auricle 

.  197 

Stifle-joint    .... 

111 

—  of  dura  mater 

.  153 

Stomach        .... 

229 

—  olfactory 

.  150 

Straight  patellar  ligaments  . 

112 

—  Valsalvae,  aortic 

.  199 

Stratified  epithelium     . 

16 

—     —  pulmonary 

.  19?) 

Strire 

12 

Sinuses  of  head    . 

.  142 

Striated  muscular  fibre 

11 

—  venous    . 

.     22 

Subarachnoid  fluid 

155 

Skeleton,  artificial 

.      7 

—  space  (of  cord) 

180 

—  natural 

.      7 

—     —      (of  brain) 

155 

Skin,  dermis 

.    17 

Subcarpal  ligament 

210 

—  epidermis 

.     17 

Subcutaneous  areolar  tissue  . 

17 

—  glands  of 

.    17 

Subject,  choice  of  a       . 

3 

—  papillated  layer  of 

.    17 

Substantia  perforata      . 

160 

—  rete  mucosum 

.    17 

Sudoriparous  glands 

18 

—  incisors  through  th 

3        .       4 

Suet 

239 

Skull,  bones  of      . 

.     24 

Sulci 

155 

Slit  of  the  external  ear 

.  123 

Superficial  abdominal  faschia  216 

Small  intestines    . 

.  233 

Superior  maxillary  sinus 

142 

Smegma  praeputii. 

.  244 

Supports  for  parts  of  subject 

6 

INDEX. 

PAGE 

Supra-renal  bodies,  see 

Pre- 

Tentorium,  ossific 

renal  bodies. 

Teres  ligament 

Suspensory  ligament,  bladder  223 

Testes  cerebri 

—     —  liver 

.  223 

—  (testicles) 

—     —  penis 

.  216 

—  coni  vasculosi  . 

Suture 

.     99 

—  coverings  of     . 

Sutures  of  skull    . 

.  102 

—  descent  of 

Sylvius,  fissure  of 

.  161 

—  epididymis 

—  aqueduct  of     . 

.  158 

—  globus  anterior 

Sympathetic  gangliated  cord  196 

— •    —  posterior  . 

— ■  nervous  system 

.     13 

—  gubernaculum 

Symphysis  maxillse  inferioris  141 

—  lobuli 

—  ischii 

.     84 

— •  mediastinum  . 

—  pubis 

.     85 

—  tunica  albuginea      . 

Synarthrosis 

.     99 

—     —  vaginalis  propria 

Synovial  fringes   . 

.     15 

—    —     —  reflexa 

—  membranes 

.     15 

—     —  vasculosa. 

—  joints 

.  100 

—  vas  deferens     . 
Thalami  optici 

Taenia  semicircularis 

.  157 

Thebesius,  foramina  of . 

Tail       . 

.  272 

—  valve  of  . 

Tapetum  lucidum 

.  149 

Thecal. 

Tarsal  cartilages   . 

.  120 

Thorax 

Tarsus 

.     92 

Thymus  gland 

Teeth    . 

.  128 

Thyroid  body 

—  canine     . 

.  129 

—  cartilage 

—  cavities  of  reserve  of       .  130 

Tissue,  yellow  elastic    . 

—  cementum 

.  129 

—  white  fibrous  . 

—  compound 

.  129 

Tongue 

—  crown  of 

.  128 

—  bone  of   . 

—  crusta  petrosa  of 

.  129 

—  fr^num   . 

—  dentine  of 

,  129 

—  mucous  membrane  of 

—  development  of 

.  130 

—  muscles  of,  extrinsic 

—  enamel  of 

.  129 

—     —  intrinsic  . 

—  incisor     . 

.  129 

—  nerves  of 

—  infundibulum  of 

.     12 

—  papillae  of 

—  milk 

.  129 

—     —  circumvallate  . 

—  molar 

.  131 

—     —  filiform     . 

—  primitive  dental  groove  .  130 

—     —  fungiform 

—  pulp,  dental    . 

.  129 

Torcular  Herophili 

—  table  of  development  of  .  121 

Trabecule  of   corpus  caver 

—  temporary 

.  128 

nosum  . 

—     —  eruptive  stage 

.  130 

—  of  spleen 

—    —  follicular  stage 

.  130 

Trachea         .         .         .176 

—     —  papillary  stage 

.  130 

Tract,  optic  . 

—     —  saccular  stage 

.  130 

Transverse  fissure  of  brain 

—     —  shedding  of 

.  130 

—     —  liver 

—  wolf's      . 

.  132 

Tricuspid  valve     . 

Tendons 

.     12 

Trochanter  major . 

Tensor  tympani     . 

.  165 

—  minor,  external 

Tentorium,  membranou 

s        .  153 

—     —  internal    . 

309 


310 

INCEX. 

PAGK 

PAGE 

Trochanteric  fossa 

.     86 

Uterus,  epithelium  of  . 

.  250 

Tube,  Eustachian 

.  138 

—  fundus  of 

.  249 

Tuber  ciuereum    . 

.  161 

—  ligaments  of    . 

.  249 

Tubercle  of  atlas . 

.     47 

—  mucous  membrane  of 

.  250 

—  lachrymal 

.     36 

—  OS  or  mouth  of 

.  249 

—  of  rib 

.     57 

Utriculus 

.  163 

—  pectineal! 

.     85 

Uvea     .... 

.  147 

—  superior  maxillae 

.     35 

Tuberculum  Loweri 

.  197 

Vagina 

.  250 

Tuberosity    . 

.     10 

Vaginal  cavities    . 

.  249 

—  of  ischium 

.     85 

—  portal  veins     . 

.  226 

Tubes,  Fallopian  . 

.  249 

—  tunics 

.  224 

—  uviniferous 

.  240 

Vagino-rectal  fold 

.  251 

—  contorted 

.  246 

—  vesical  fold 

.  251 

—  seminiferous    . 

.  246 

Valsalva,  sinus  of 

.  199 

Tunica  adiposa  renalis  . 

.  239 

Valve,  bicuspid     . 

.  199 

—  albuginea  testis 

.  246 

—  Eustachian 

.  197 

—  Jacobi      . 

.  148 

—  ileo-caecal 

.  233 

—  nervosa    . 

.  148 

—  mitral      . 

.  199 

• —  "Ruyschiana 

.  147 

—  semilunar  aortic 

.  199 

—  vaginalia  scroti 

.  224 

—     —  pulmonary 

.  198 

—     —  testis 

.  224 

—  of  Thebesius    . 

.  197 

■ —  vasculosa  retinae 

.  148 

—  tricuspid 

.  198 

—     —  testis 

.  246 

—  of  veins   . 

.     22 

Turbinated  bones  . 

.     33 

—  of  Vieussens     . 

.  158 

Tushes .         .         . 

29,  132 

Varolii,  pons 

.  159 

Tympanic  cavity  . 

.  164 

Vas  deferens 

.  247 

—     —  ossicula  of 

.  164 

Vasa  afferentia 

.     23 

—  efPerentia 

.     23 

Umbilical  artery  . 

.  253 

—  recta 

.  246 

—  cord 

.  253 

—  vasorum 

.     20 

—  region  of  abdomen 

.  231 

Vascular  coronary  secretin 

g 

—  vein 

.  253 

substance 

.  278 

TJnstriated  muscular  fil 

)re      .     11 

—  laminae    . 

.  279 

Urachus 

.  255 

Vasculosa,  tunica 

.  148 

Ureters 

.  240 

Vegetative  nervous  system 

.     13 

Urethra  (male) 

.  242 

Veins    .... 

.     21 

—  fossa  navicularis 

.  243 

—  valves  of 

.     21 

—  lacunse  of 

242 

—  axillary 

.  207 

—  mucous  membrane  < 

if       !  242 

—  azygos 

.  193 

—  membranous    . 

.  242 

—  brachial,  superficial 

.  207 

—  prostatic 

.  242 

—  bronchial 

.  192 

—  spongy    . 

.  243 

—  cardiac    . 

.  200 

Urinary  bladder    . 

.  241 

—  cava  anterior  . 

.  193 

Uriniferous  tubes 

.  240 

—     —  posterior  .         .    193,  238 

Uterus 

.  249 

—  cephalic 

.  207 

—  artery  of 

.  238 

—  corouary 

.  200 

—  body  of    . 

.  249 

—  circumflex,  of  ilium 

.  265 

—  cavity  or 

.  249 

—  diaphragmatic,  see  Phrenic. 

cervix  of 

.  249 

—  femoral    . 

.  265 

—  cornua  of 

.  249 

—  of  foot     . 

.  215 

INDEX. 


311 


Veins,  hepatic 

—  humeral 

—  iliac,  common 

—  —  external 

—  —  internal 

—  intercostal 

—  interlobular 
— •  intralobular 

—  jugular    . 

—  lingual     . 

—  lumbar     . 

—  mesenteric,  anterior 

—  posterior 

—  metacarpal 

—  metatarsal 

—  phrenic    . 

—  plat 

—  portal 

—  pulmonary 

—  renal 

—  saphenous 

—  spermatic 

—  spiral 

—  splenic     . 

—  sublobular 

—  tibial 

—  vaginal,  portal 

—  varicose,  of  face 
Velum  pendulum  palati 
Vena  cava,  anterior 

—  —  posterior 

—  portas     . 
Venffi  Galeni 

—  vorticosEB 
Venous  sinuses 
Venter  scapulae     . 

—  ilii 

Ventricles  of  larynx 
Ventricle,  fifth 

—  fourth 

—  lateral     . 

—  left  (heart)      . 

—  right  — 

—  third 
Vertebrse,  cervical 

—  coccygeal 

—  dorsal 

—  false 


193 


PAGE 

226 
207 
265 
265 
265 
187 
226 
226 
172 
136 
239 
228 
228 
215 
271 
239 
207 
226 
198 
239 
60 
239 
207 
236 
226 
271 
226 
118 
138 
193 
,238 
226 
153 
147 
22 
63 
84 
176 
156 
158 
156 
199 
198 
158 
46 
56 
50 
44 


PAGB 

.     52 

.  54 
.  43 
.  42 
.  42 
.  103 
.  103 
n. 
.  242 


Vertebra?,  lumbar 

—  sacral 

—  true 

—  typical     . 
Vertebral  segments 

—  articulations    . 

—  ligaments 

—  column,  see  Spinal  colum 
Vena  montanum  . 
Vesica  urinaria,  see  Bladder. 
Vesi(;les,  germinal          .  .  248 

—  Graafian .         .         .  .248 

—  seminal  ....  247 
Vestibule  .  .  .  .162 
Vidian  nerve  .  .  .  127 
Vieussens,  valve  of  .  .  158 
Villi  of  bowels  .  .  .232 
Villous  layer  of  stomach  .  230 
Vitreous  humour            .  .  149 

—  tables  .  .  .  .150 
Vocal  cords  ....  175 
Voluntary  muscle  .  .  125 
Vomer  .  .  .  .39 
Vulva 251 

—  commissures  of         .  .  251 

—  erectile  tissue  of      .  .  251 

—  fossa  navicularis  of  .  251 

—  labia  of   .         .         .  .251 

—  mucous  membrane  of  .  251 

Wall  of  hoof          .         .  .  274 

"Water  bag"        .          .  •  255 

Wharton's  duct     .         .  .132 

White  muscular  fibre    .  .     11 

—  nerve  fibres     .         .  .14 

—  substance  of  Schivann  .  14 
Wilson's  muscle  .  .  .  242 
Winslow's  foramen  .  223,  230 
Womb,  see  Uterus. 

Wrist,  see  Carpus. 

Xiphoid  cartilage           .  .     60' 

Zima,  zonula  of     .         .  .  144 

Zona  pellucida       .         .  .  248 

Zonula  cilaris  {v  Zinnii)  .  149 

Zygoma         .         .         .  .31 

Zygomatic  ridge   .         .  .35 

—  bone        .        .        .  .38 


ERRATA. 

Page    20. — Line  42, /or  circular  read  circulus. 

34. —     „      ^,for  incisorium  read  incisorum. 

41. —     „    12,  for  carinus  read  caninu?. 

59. — Lines  41  and  44, /or  scalenius  read  scalenus. 

76. — Line  33,/or  unciform  read  unciforme. 

80. —     „    38, /or  sessamoid  read  sesamoid. 
108. —     „    21, /or  suffraginis,  read  coronse. 
129. —     „    12,/or  infundibuli  read  infundibula. 
178. —     „    2^,  for  scalenius  read  scalenus. 


PEIKTED    EY   J.    E.    ADLAltD,    BAlil  llOLUiltW    CLOSJt. 


iJi 


Webster  Family  Library  of  Veterinari/  Medicine 
Cummings  Schoo!  of  Veterinary  Medicine  at 
Tiifis  University 
200  Westboro  Road 
NorthGr^ftnn  MAOIBSR 


